The weapon masteries meet my general expectations. They are a simple, straight forward bolt-on that patches rather than fixes some of the issues with weapons/martials in 5e. Would another system be better? Probably. This is way better than what we currently have though, and for a backwards compatible upgrade. This 5.5 edition was never going to be a cure-all. I think this will be lessons learned for the eventual 6e. For now, it's good enough and it's surveyed really well. They literally have been given no reason to revisit it, as the feedback appears to have indicated that the rules as presented were a home run.,
The overall positive feedback for Weapon Mastery might be biased to the point that people were happy with any aid given to martial classes and perhaps the prospect of weapon choice being more meaningful. The only negative response was to Flex which by JC's words was meant as an easy-to-approach mastery for newcomers, just a straight damage buff to sword-and-board players. For more experienced players this was the least interesting property because it didn't really change anything, except muddy the waters between a few one-handed weapons dealing the same damage as half of the two-handed weapons and effectively removing the versatile property from those weapons.
I do agree that it is unlikely for the DnD team to whip up a new system or do particularly much about Weapon Masteries at this point in preparation for 5.5e. The proposed macro system for martial classes to get more tactical actions is likely more feedback for an eventual 6e.
On a related note in regards to a feat overhaul for an eventual 6th edition:
I once had a misunderstanding about what it would mean to implement the Background feats and how it were going to work for 5.5e. I thought they aimed to completely remove the ASIs and overhaul the feats to only have half-feat options (aka +1 stat and some feat bonus, often tied to that stat or stat group). There's a couple of really impactful problems with that approach but also an insane amount of potential for customization. The problems ranges from not getting enough stat increases over time, to resulting in more homogenous characters, to feats only making sense as a package, to problems about keeping track of all your extra features.
The stat increase problem is mostly evident where most classes only gets 5-6 ASIs or in this case 5-6 half feats for +5-6 stats, meaning you generally only get to increase your main stat to 20 and nothing else. The problem about homogenous characters stems from a design issue where if a set of good-stuff feats exists, it may result in very similar character creations, removing the appeal of a vaster customization system - the requirement for very good balancing is high to achieve success on this parameter. Then we have feats which generally only makes sense as a full package - although looking through the feat list I don't really see many feats which are divided into multiple sub-benefits which couldn't make sense to split up. There's obviously feats like Magic Initiate that cannot be split up and making it into a half feat would... most likely make it a lot stronger than many other feats, but there may be solutions to that too.
The benefit of only having half feats would be that your character gets to improve on the path you set out for them. Right now most players build their character around class features and uses ASIs to get +2 stat to as quickly as possible get to max stats in their main stat(s). Feats really need to bring a LOT to the table to be considered over a +2 stat increase or your character is not very dependent on your stats. To me this feels a little bit boring and often makes feats overlooked.
Some solutions to the problems at hand could be to increase the amount of feat acquisitions you get over the course of class levels - and perhaps tie it to character level rather than class levels. As for securing different builds and avoid homogeny, the feats need to be balanced quite a bit more than what the 5e feats are at present. One major benefit here is that you can practically reiterate on feats quite easily without breaking up class structures. You can also work with prerequisites more and as a tie-in to the problems of feats as packages and also "packed" feats that would be very strong as half-feats; you could make entry-level feats followed by one or more medium-level and/or a mastery/high-level feat progression. Just to make a quick example see the spoiler below.
Imagine Great Weapon Master which has the following two benefits:
On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.
Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.
Then we split that up into two half-feats:
Battle Fury (no prerequisites)
Increase your Strength, Dexterity, or Constitution score by one, to a maximum of 20. If you are level 18 or above this maximum increases to 22.
On your turn, when you score a critical hit with a melee weapon or reduce a creature to 0 hit points with one, you can make one melee weapon attack as a bonus action.
.
Great Weapon Master (requires Battle Fury)
Increase your Strength score by one, to a maximum of 20. If you are level 18 or above this maximum increases to 22.
Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.
Every martial class may be tempted to pick up Battle Fury, but only those who have heavy weapons are interested in Great Weapon Master. Now I get that the devs have chosen to remove both GWM and SS in 5.5, but this was just a well-known feat with an easy-to-chop-up structure that could showcase how it could look like. Battle Fury might also be a prerequisite to another feat, lets just say Improved Critical Hit (yes I know, Champion thing) that grants +1 STR/DEX and your melee weapon attacks can score a critical hit on a die roll one number lower - aka if you get more features of similar style, they stack. Perhaps there's also a "mastery"-feat above that requires Improved Critical Hit and character level 10+ and lets just keep stealing and say Brutal Criticals that adds +1d10 to your critical damage rolls. Now there's a package of feats that makes sense together but functions as individual, although interdependent, feats. There may be some exclusions so one entry-level can only be progressed to one medium-level and again to one high-level. So you cannot pick up Battle Fury and then both Great Weapon Master and Improved Critical Hit.
This half-feat system would also remove the "need" for tacked-on benefits we see in some feats where it doesn't serve the main purpose of the feat but without the extra benefit the feat felt not significant enough to pick. Mobile comes to mind that grant +10 ft. movement, removes penalty from moving over difficult terrain and if you hit someone they cannot trigger opportunity attacks against you. This feat makes sense as a package under the name, but there's no issue in splitting it up into half-feats. Similar could be said about something like Sentinel.
A feat like Charger, well hopefully a revised version of it that would grant bonus damage to your next weapon attack after moving a certain distance (not needing to use the dash action but could easily keep the bonus action attack if you do take the dash action) probably would look more favorable if it had the half-feat treatment and a less strict requirement to apply its benefit. It could even have an upgrade or a mastery feat that makes your character able to dash and slice in combat - perhaps with a skill check for athletics/acrobatics to keep it going. Basically imagine you're doing drive-by attacks while running back and forth through the enemy, then use your athletics to either outrun their reflex to make an opportunity attack or acrobatics to evade it (both just meaning you wont trigger opportunity attacks) and a failed check has some kind of penalty - perhaps just to trigger the opportunity attack and end the ability to attack further that turn. Perhaps this also requires the Mobile feat (revised to just give +10 ft. movement and +1 stat).
.
I feel like a lot could be made with such a system, but the success or fall is generally on how well you can balance the choices, drawbacks and progressions. Alas that is for a new edition to make.
Edit: To comment on the frustrations of players slowing down play (usually from the abundance of actions/spells available and poor understanding, preparation or memory of their options):
I get that pacing is important to keep the game rolling, but you should also realize that you might be removing some of the roleplay aspect of certain situations by being impatient - not to say that is the case in the scenario you mentioned. Honestly if we have an Indiana Jones and the golden monkey scenario, I hope the DM punishes (maybe even severely) the impatient Barbarian (and possibly their team) who just go "rock smash!" instead of approaching the situation as an obstacle that might require a different approach than the most obvious one - as in just going up and grabbing the monkey. There are certainly situations where players overanalyse a situation without need. But it is often difficult to know when it's right to overanalyse and avoid getting smashed by a boulder or avoid a demon trap or get caught in an ambush, and when it's just a shrine without any nefarious traps or curses or anything harmful.
I believe there's also a vast difference between waiting for someone to make a decision and the group discussing what actions they should take. Waiting is just wasted time, whilst discussions are one of the major reasons why we choose to meet up with a group of fellow nerds to play vividly in our own fantasy. If that's not something the player is interested in I think there's a mismatch between expectations from the player to the playgroup.
I do hope that it is possible to discuss in your respective playgroups that people who slow down play because they are poorly prepared... maybe shouldn't play advanced characters that require more dedication and preparation than others. Or like Bearbug mentions get assisted by the DM (or anyone really) to narrow their choices down to a select few they can remember and usually gets them by. They are obviously free to use their other spells/feats/whatever if they don't hold up the game. And repeated offenses treated with brutal cut-offs is acceptable in my eyes (we do still want to be friends though).
If I hold up my playgroup it is usually a matter of ruling or decisions in tight combat encounters (read deadly). Depending on how a certain spell, condition, action, whatever functions it can have a significant impact on whether it makes sense to do and if it might make a significant effort for the team to overcome an obstacle.
.
I do believe that part of this supposed impatience could be from a lack of options on their own character. It is easy to get impatient when you only have a few choices to make and don't get why others are taking longer to make their decisions.
.
I remember my playgroup once tried blitz-combat - aka we found a 10 second hour glass and if your actions weren't rolling before the sand ran out you were skipped as your character was frozen in shock. Aka if you're just waiting for 10 seconds without anything happening you were skipped. If you started your actions and didn't hold long breaks you could keep going. It was largely impractical and on occasion not enforced as players called for extensions but it was fun to challenge yourself to make decisions so quickly with minimal time to absorb what happened on the battlefield and what your optimal course of action might be. However as many games where your decision-making might be complex and you're forced to not be able to consider your plan of action, it gets a bit frustrating, especially for more complex characters.
The best balance is just to be respectful of each others time. Both to keep the game flowing and allow players to utilize their character, and allow the group the ability to discuss and hopefully roleplay.
The overall positive feedback for Weapon Mastery might be biased to the point that people were happy with any aid given to martial classes and perhaps the prospect of weapon choice being more meaningful. The only negative response was to Flex which by JC's words was meant as an easy-to-approach mastery for newcomers, just a straight damage buff to sword-and-board players. For more experienced players this was the least interesting property because it didn't really change anything, except muddy the waters between a few one-handed weapons dealing the same damage as half of the two-handed weapons and effectively removing the versatile property from those weapons.
I do agree that it is unlikely for the DnD team to whip up a new system or do particularly much about Weapon Masteries at this point in preparation for 5.5e. The proposed macro system for martial classes to get more tactical actions is likely more feedback for an eventual 6e.
On a related note in regards to a feat overhaul for an eventual 6th edition:
I once had a misunderstanding about what it would mean to implement the Background feats and how it were going to work for 5.5e. I thought they aimed to completely remove the ASIs and overhaul the feats to only have half-feat options (aka +1 stat and some feat bonus, often tied to that stat or stat group). There's a couple of really impactful problems with that approach but also an insane amount of potential for customization. The problems ranges from not getting enough stat increases over time, to resulting in more homogenous characters, to feats only making sense as a package, to problems about keeping track of all your extra features.
The stat increase problem is mostly evident where most classes only gets 5-6 ASIs or in this case 5-6 half feats for +5-6 stats, meaning you generally only get to increase your main stat to 20 and nothing else. The problem about homogenous characters stems from a design issue where if a set of good-stuff feats exists, it may result in very similar character creations, removing the appeal of a vaster customization system - the requirement for very good balancing is high to achieve success on this parameter. Then we have feats which generally only makes sense as a full package - although looking through the feat list I don't really see many feats which are divided into multiple sub-benefits which couldn't make sense to split up. There's obviously feats like Magic Initiate that cannot be split up and making it into a half feat would... most likely make it a lot stronger than many other feats, but there may be solutions to that too.
The benefit of only having half feats would be that your character gets to improve on the path you set out for them. Right now most players build their character around class features and uses ASIs to get +2 stat to as quickly as possible get to max stats in their main stat(s). Feats really need to bring a LOT to the table to be considered over a +2 stat increase or your character is not very dependent on your stats. To me this feels a little bit boring and often makes feats overlooked.
Some solutions to the problems at hand could be to increase the amount of feat acquisitions you get over the course of class levels - and perhaps tie it to character level rather than class levels. As for securing different builds and avoid homogeny, the feats need to be balanced quite a bit more than what the 5e feats are at present. One major benefit here is that you can practically reiterate on feats quite easily without breaking up class structures. You can also work with prerequisites more and as a tie-in to the problems of feats as packages and also "packed" feats that would be very strong as half-feats; you could make entry-level feats followed by one or more medium-level and/or a mastery/high-level feat progression. Just to make a quick example see the spoiler below.
Imagine Great Weapon Master which has the following two benefits:
Then we split that up into two half-feats:
Battle Fury (no prerequisites)
.
Great Weapon Master (requires Battle Fury)
Every martial class may be tempted to pick up Battle Fury, but only those who have heavy weapons are interested in Great Weapon Master. Now I get that the devs have chosen to remove both GWM and SS in 5.5, but this was just a well-known feat with an easy-to-chop-up structure that could showcase how it could look like.
Battle Fury might also be a prerequisite to another feat, lets just say Improved Critical Hit (yes I know, Champion thing) that grants +1 STR/DEX and your melee weapon attacks can score a critical hit on a die roll one number lower - aka if you get more features of similar style, they stack. Perhaps there's also a "mastery"-feat above that requires Improved Critical Hit and character level 10+ and lets just keep stealing and say Brutal Criticals that adds +1d10 to your critical damage rolls.
Now there's a package of feats that makes sense together but functions as individual, although interdependent, feats.
There may be some exclusions so one entry-level can only be progressed to one medium-level and again to one high-level. So you cannot pick up Battle Fury and then both Great Weapon Master and Improved Critical Hit.
This half-feat system would also remove the "need" for tacked-on benefits we see in some feats where it doesn't serve the main purpose of the feat but without the extra benefit the feat felt not significant enough to pick. Mobile comes to mind that grant +10 ft. movement, removes penalty from moving over difficult terrain and if you hit someone they cannot trigger opportunity attacks against you. This feat makes sense as a package under the name, but there's no issue in splitting it up into half-feats. Similar could be said about something like Sentinel.
A feat like Charger, well hopefully a revised version of it that would grant bonus damage to your next weapon attack after moving a certain distance (not needing to use the dash action but could easily keep the bonus action attack if you do take the dash action) probably would look more favorable if it had the half-feat treatment and a less strict requirement to apply its benefit. It could even have an upgrade or a mastery feat that makes your character able to dash and slice in combat - perhaps with a skill check for athletics/acrobatics to keep it going. Basically imagine you're doing drive-by attacks while running back and forth through the enemy, then use your athletics to either outrun their reflex to make an opportunity attack or acrobatics to evade it (both just meaning you wont trigger opportunity attacks) and a failed check has some kind of penalty - perhaps just to trigger the opportunity attack and end the ability to attack further that turn.
Perhaps this also requires the Mobile feat (revised to just give +10 ft. movement and +1 stat).
.
I feel like a lot could be made with such a system, but the success or fall is generally on how well you can balance the choices, drawbacks and progressions. Alas that is for a new edition to make.
Edit: To comment on the frustrations of players slowing down play (usually from the abundance of actions/spells available and poor understanding, preparation or memory of their options):
I get that pacing is important to keep the game rolling, but you should also realize that you might be removing some of the roleplay aspect of certain situations by being impatient - not to say that is the case in the scenario you mentioned. Honestly if we have an Indiana Jones and the golden monkey scenario, I hope the DM punishes (maybe even severely) the impatient Barbarian (and possibly their team) who just go "rock smash!" instead of approaching the situation as an obstacle that might require a different approach than the most obvious one - as in just going up and grabbing the monkey.
There are certainly situations where players overanalyse a situation without need. But it is often difficult to know when it's right to overanalyse and avoid getting smashed by a boulder or avoid a demon trap or get caught in an ambush, and when it's just a shrine without any nefarious traps or curses or anything harmful.
I believe there's also a vast difference between waiting for someone to make a decision and the group discussing what actions they should take. Waiting is just wasted time, whilst discussions are one of the major reasons why we choose to meet up with a group of fellow nerds to play vividly in our own fantasy. If that's not something the player is interested in I think there's a mismatch between expectations from the player to the playgroup.
I do hope that it is possible to discuss in your respective playgroups that people who slow down play because they are poorly prepared... maybe shouldn't play advanced characters that require more dedication and preparation than others. Or like Bearbug mentions get assisted by the DM (or anyone really) to narrow their choices down to a select few they can remember and usually gets them by. They are obviously free to use their other spells/feats/whatever if they don't hold up the game. And repeated offenses treated with brutal cut-offs is acceptable in my eyes (we do still want to be friends though).
If I hold up my playgroup it is usually a matter of ruling or decisions in tight combat encounters (read deadly). Depending on how a certain spell, condition, action, whatever functions it can have a significant impact on whether it makes sense to do and if it might make a significant effort for the team to overcome an obstacle.
.
I do believe that part of this supposed impatience could be from a lack of options on their own character. It is easy to get impatient when you only have a few choices to make and don't get why others are taking longer to make their decisions.
.
I remember my playgroup once tried blitz-combat - aka we found a 10 second hour glass and if your actions weren't rolling before the sand ran out you were skipped as your character was frozen in shock. Aka if you're just waiting for 10 seconds without anything happening you were skipped. If you started your actions and didn't hold long breaks you could keep going. It was largely impractical and on occasion not enforced as players called for extensions but it was fun to challenge yourself to make decisions so quickly with minimal time to absorb what happened on the battlefield and what your optimal course of action might be.
However as many games where your decision-making might be complex and you're forced to not be able to consider your plan of action, it gets a bit frustrating, especially for more complex characters.
The best balance is just to be respectful of each others time. Both to keep the game flowing and allow players to utilize their character, and allow the group the ability to discuss and hopefully roleplay.