Update: Added consideration for solo play, changes using resources from forgotten realms: heroes of faerûn that may suit organized play, optional recommendation and elaborated main strategy.

Hi, welcome to the thread. Just wanna talk about some classes and how their roles may change and stuff. I dislike feeling underprepared and don't mind stuff going unused.

My bias casually playing with the same dungeon master (DM) over years makes my experience sorta unique with this game since much changes with a different DM. The first time one of my characters met their end was at 8th level in the previous 5e ruleset from 2014. We've now reached 9th level on the most updated 5e ruleset of 2024 and I like how some features may contribute to a satisfying result in a fight. "Your opposition may be stronger, but you're smarter" -My mom. "Killing is art, dying is part (of it)" -An online player.

People say best crowd control is to quickly reduce target's hit points (HP) to zero or best defense is a strong offense and I wanna point out some DMs do that against player characters (PC). Your PC may end up relying on opponents' whims if high damage dealing allies are unconscious due to missing all their hit points, which is why I may overvalue features that prevent or reduce damage taken and/or quickly regain HP. I believe these classes should be in a group for the 5th edition ruleset of 2024 according to what I've experienced with my DM over time:
1. Barbarian
2. Cleric
3. Wizard
4. Bard
5. Paladin

0. Rage, preserve life channel divinity, buncha odd magics, spell backup and aura of protection. Monsters will try to defeat PCs while resistances granted by barbarian's rage lower damage character takes, main thing I need you to note is that it doesn't decrease the amount of healing, so the HP of an enraged barbarian will last noticeably longer in battle compared to the HP of other allies lacking damage resistances (unless PC's armor class is high enough for enemies to rarely hit or they fight beyond opponent's reach). Healing enraged HP that have appropriate damage resistances makes them withstand over double damage due to round down; 41 damage of a resisted damage type becomes 20 damage that only needs 20 healing instead of 41, which means all healing is indirectly worth more than double for a resistance. Wizard needs to get creative (I really mean "need" instead of "should"), procure wizard rituals from other spellbooks or scrolls (false life spell can provide about 9 average temporary HP, which is a lot at 1st PC level). Bards can scout more effectively due to their expertise and jack of all trades (unless they're low on HP, if that's the case, focus on recovering), they may learn the cure wounds spell and nudge cleric to concentrate on the beacon of hope spell. If there's room for another PC, a paladin's aura of protection and their possible concentration on the bless spell can shore up some PCs saving throws. This setup can be low on damage output, but may endure long enough to conquer challenges.

Build recommendations using player's handbook 2024 and forgotten realms: heroes of faerûn while attempting organized play compatibility: 1. Aasimar species 15+2=17 strength with ice fisher (background), alert (origin feat), path of the wild heart (subclass) bear rage of the wilds for more damage resistances (effective double healing efficiency for resisted damage types) combined with aasimar's, great weapon master (general feat) 17+1=18 strength; if going to experience 9th PC level, there's polearm master (general feat) 18+1=19 strength at 8th to try brutal strike with bonus action provided by the feat since it would deal lower damage on a hit anyway; if playing 14th with lion power of the wilds, an option is sentinel (general feat) 19+1=20 strength at 12th for unarmed strike halt when holding reach weapon; +2 constitution for 16th since PC should already have 20 strength-increase strength if that's not the case; recovery (epic boon) to regain half max HP once per long rest if 11th level's relentless rage fails (greater constitution improves odds of it working + increases max HP), check with DM if you're allowed to use epic boon's d10s outside of combat so you attack more with polearm master instead of using bonus action to self-heal, if you can only use them in combat, start off with heavy 2d6 weapon until you spend them all, then switch to heavy reach d10 weapon.

2. Ever since the total party kill (TPK) to fireball spam at 10th PC level a while back I kinda like having fire resistance on my PCs which also work against allies' fireballs, so a high wisdom fire resistant dragonborn species suits me here; they can also unlock fly speed upon leveling like aasimar. Alert (origin feat), protector divine order, life domain (subclass), war caster (general feat) to improve concentration, potent spellcasting, resilient constitution (general feat) to improve concentration, maybe tough (origin feat) before desperate resilience (epic boon). Concentration bless, calm emotions, spirit guardians, beacon of hope, circle of power, conjure celestial, etc. Consider healing word, dispel magic, heal, mass heal.

3. The feeblest HP of all, high intelligence human species for tough besides alert (origin feats), abjurer (subclass), war caster (general feat) to improve concentration, resilient constitution (general feat) to improve concentration, intelligence as high as possible, desperate resilience (epic boon). False life (spell) for low level PC with blade ward (cantrip), mage armor and shield (spells) may be postponed and acquired through 3rd PC level abjuration savant, see invisibility, darkvision, rope trick, fireball, phantom steed, mordenkainen's faithful hound, dimension door, tasha's bubbling cauldron, contingency otiluke's resilient sphere, finger of death, teleport, mind blank, prismatic wall, wish, concentration witch bolt, cloud of daggers, spider climb, fly, polymorph, wall of force, circle of power, yolande's regal presence, shapechange, signature spells fly, counterspell to cast without slot on same turn as something else once per short rest when enemy tries counterspell may counterspell their counterspell without using spell slot on the turn you cast the initial spell. Counterspell and dispel magic are always prepared at 10th abjurer level. Maybe get some spell scrolls.

4. Dwarf species (120 feet darkvision, higher HP, resistance to poison traps), at least 15+0=15 charisma, stuff from life domain cleric + abjurer wizard (research the subclasses to support them like counterspell enemy's counterspell, upcast cure wounds while concentrating on beacon of hope, dimension door ally across wall of force, concentrate on fly so wizard may concentrate on something else depending on situation, etc), alert (origin feat) to reposition when ambushed while scouting close enough for party to effectively join combat, college of lore (subclass) for magical discoveries they really make a difference (chill touch, counterspell, aura of life, etc), war caster (general feat) to improve concentration, resilient constitution (general feat) to improve concentration, charisma as high as possible, desperate resilience (epic boon). Consider conjure woodland beings (spell), expertise perception, sleight of hand, acrobatics, investigation, proficiency arcana, stealth, survival, insight, thieves' tools (from background).

5. High charisma fire dragonborn species, alert (origin feat), blind fighting (fighting style) to overcome lack of sight (blindness, invisibility, etc), oath of devotion (subclass) to protect against the charmed condition (there's also the mind blank 8th level spell and the calm emotions concentration spell to protect against it) + get charisma modifier bonus to hit with melee sacred weapon channel divinity, war caster (general feat), charisma as high as possible (ideally 20 charisma at 12th PC level) try getting wizard or bard to share potion of hill giant strength from tasha's bubbling cauldron (spell) near 11th PC level, purple dragon commandant (general feat) at 16th PC level, desperate resilience (epic boon).

Optional celestial patron warlock (fire dragonborn for the resistance ^-^ faced level-adjusted lava with fireballs at 8th PC level in 2025 without warning and every ally survived, flying above lava without concentration is useful) can use pact magic to upcast cure wounds, aid (spells), and access a feature similar to inspiring leader (general feat) at 10th level called celestial resilience. I would prefer another dwarf bard to switch scouting when at low HP, plus they could use bardic inspiration on each other, making d20 tests even more feasible. Eldritch invocations, if keeping warlock, are pact of the blade, agonizing eldritch blast, lessons of the first ones purple dragon rook needed for 16th level general feat, thirsting blade, eldritch smite, lifedrinker, devouring blade, witch sight, pact of the tome acid splash mage hand starry wisp find familiar tenser's floating disk, gift of the protectors, spells like armor of agathys, hex, tasha's hideous laughter, fly, dispel magic, dimension door, synaptic static, tasha's bubbling cauldron, foresight with rashemi wanderer (background) 15+2=17 charisma tough (origin feat), spell sniper 17+1=18 charisma at 4th PC level, great weapon master at 8th, 18+2=20 charisma at 12th, purple dragon commandant at 16th using lessons of the first ones eldritch invocation, desperate resilience (epic boon). Remember 13 strength for heavy melee weapons and 13 dexterity for heavy ranged weapons.

Consideration for solo play: There is strength in numbers. "Ape alone... Weak. Apes together... Strong." -Caesar. Hire trustworthy adventurers (non-playable characters) to back you up on your journey if possible. You may also be able to lure a conflict into a stronger force that will fight them.

Barbarians are not as good as tanks as you think. The main downside is the lower AC compounded by advantagebto attack them.  This means they take more damage, eat more riders and require more resources to heal.  The one advantagebthey have is damage  making them an easy target but resistance and hp are worse survival.mechanics than AC.

You see AC is the only one that gets better the more you have. So combining Armor, Shield, Fighting Style plus spells can make you better at survival than any Barb.  What you need is damage to keep the monsters attention, something like grappling, smites or control options.

That was really long to read, and I will admit I didn’t, but I have to take issue with one of your early statements. The best crowd control isn’t taking opponents hp, it’s taking their action economy. 
Fireball is great for hurting lots of enemies at once, but they still will all be standing afterwards. Hypnotic pattern, however, is basically pressing the “we win” button.
If an enemy doesn’t have ranged attacks, levitate is possibly the best 2nd level spell to use on them. Banishment, hold monster, monk’s stunning strike, etc. Even pausing their attacks for one round can give you enough room to turn the fight.

For solo play I think fighters are fine.  Some self-heals to keep moving and a lot more available in 2024.  An Eldritch knight can add Arcane Recovery.   About half as much healing available as a paladin at 6th when comparing Second wind versus lay on hands.  High AC+ shield.  More feats or ASI to help.

You say solo then mention "if cleric doesn't get it."  Solo characters will absolutely survive at the whim of a DM because any single character can be super easily countered.  It is impossible to create a character a DM cannot kill.  If your DM spams fireballs at you, next time they will spam lightning bolts.  Or Hold Person. 

Non-solo characters should meet a party goal.  It's hard to beat a martial (fighter/barb/pally), caster (Wizard/sorc/bard), cleric/druid, and skill (Rogue/bard/maybe ranger) party.

Happy Halloween everyone,

@Taenx If AC can reliably block opponent's bonus to hit they likely have lower AC, HP and won't pose much of a threat in a deadly encounter which a creature may be expected to hit 25 AC with disadvantage and take over a third of character's HP without scoring a critical hit.

@Xalthu True, zero HP usually prevents creature from taking actions in the 2024 ruleset.

@Burgen_Badluk; @Tigero Good insight, I admit I have little experience playing without a team. The more we play the more we learn when a fight is winnable or not and the group back then did not fully understand some battles were too heavily stacked against characters, including the DM.

Quote from Xalthu >>

That was really long to read, and I will admit I didn’t, but I have to take issue with one of your early statements. The best crowd control isn’t taking opponents hp, it’s taking their action economy. 
Fireball is great for hurting lots of enemies at once, but they still will all be standing afterwards. Hypnotic pattern, however, is basically pressing the “we win” button.
If an enemy doesn’t have ranged attacks, levitate is possibly the best 2nd level spell to use on them. Banishment, hold monster, monk’s stunning strike, etc. Even pausing their attacks for one round can give you enough room to turn the fight.

 Hypnotic Pattern really is overpowered, at least in multi-target fights. Psychic Scream is also a good crowd-control spell. 9th-level fireball that requires an int save and stuns for a minute.

I admit I am confused by your response.  I do not know what you mean by expected to hit AC 25 with disadvantage, do you mean 50% of the time? 75%? 

Consider the only creature that can consistently (< 50% of the time) hit AC 25 with disadvantage is the Tarrasque.

Are you saying a character with a 25 AC would not contribute to a fight?

Hi, before replying I wish everyone a happy thanksgiving prep for the upcoming day after tomorrow (my country doesn't celebrate) :3

@Taenx I did an experiment on my own after a particularly difficult encounter I felt the DM let us win so they could crush us on a harder fight later on. It was 'how many rounds my ideal character at the time would survive using AC against a heavy hitting enemy' and I disliked the result after 1v1 them on a white room exchanging blows as both creatures. I didn't register scientific data, but got the feeling AC wasn't what I was looking for to deal with heavy hitter types. AC will be a lot more useful against multiple light hitters that have less chance to hit and, when they do, damage isn't very much. DM often uses 3rd party creatures that aren't in the Monster Manual and, as one of the results, I get less chances to review and experiment after a battle. They change creature appearance and name, maybe to discourage people from looking up weaknesses on the spot, which I don't think happens in our group and, if it did, the guy hasn't been showing up to play.

We broke a new group record last Sunday! We reached 9th character level with zero deaths for the first time ever after playing casually for years and I count that as a win, no matter how small that may seem x) DM says it's them vs the players, 'stakes aren't high enough otherwise'. We may get an average of two combat encounters every session. I'm aware there are groups that go multiple sessions with zero combat encounters and some won't play if their character's life isn't protected by the DM. I enjoy the challenge.

Barbarians are excellent melee dps, but they suffer from being melee, they just don't have good ranged options and, while it's not as pronounced as 2014, kiting still wins a lot of battles.