So, since, for some reason, you made it so we can't edit monsters, or anything else, we have to make a copy of an existing monster if we want to modify it at all. 

So, I made a copy of Skeleton, because i don't want every skeleton to have the same weapons and armor and HP. But, I'd like to build on that to make other new ones that already have the armor i put on my first one. Can't do that, have to start over from the basic Skeleton.  It just seems like this tool is not user friendly at all.

It really seems like there's no good reason why i should not be able to start from a creation of my own and base a new item or monster or background or whatever on that.

ALSO: Why can't we modify monsters? Once they are added to the encounter, we should be able to modify each one individually. Not eveyr goblin in the entire world has the same weapon.

ALSO: You made it so we can make new magical items, and that's nice, but why not make it so we can make new items that are mundane. Like a cloak, a cape, a helmet, gauntlets, or anything we want that is not already in the extremely limited list from the PHB?

 You can use your own monsters as templates for new monsters with the "Create a New Monster" under the homebrew section of collections. 

Also for a lot of the more particular editing I would consider just keeping track of it in your notes, rarely is the damage different enough to require changing their actions. If they're using a very different weapon than usual you could just mentally keep track of that weapons qualities. 

I would wager the reason mundane homebrew items aren't implemented is that a large majority of the features of the homebrew system are the features the dndbeyond team uses to make items as well. However, there isn't a reason for them to create equipment that way since all "RAW" equipment comes as is, or is a magic item. So a lot of that ends up hardcoded. 

To address your first point, it is possible to edit homebrew, the how just depends on if it's published or not

For unpublished homebrew, there should be an Edit link in the top right when viewing your creation, next to 'Share With Community' and 'Delete'. Clicking that will take you to the edit screen.

Due to how publishing homebrew content works, and the desire not to break or unintentionally affect character sheets that have added it, editing published works slightly differently. For your published homebrew, you'll see 'Create New Version' next to 'Disable Comments'. Click that

If you now return to your homebrew creations, you'll see two versions of your homebrew; one published and one not.

Make your changes to the unpublished version (including increasing the version number) and then publish it. It will 'replace' the older version, although it won't affect anyone who has already added the older version. This is intentional and to prevent unwanted changes to character sheets.

As for your point about making copies of existing homebrew, I can assure you that's possible too. For example, here are the two versions of the above item, both able to be copied:

Regarding monsters, you can homebrew your own variants and add them to the encounter builder (Edit: as sorce points out, don't publish monsters with minor edits), but a Monster Builder is on the roadmap as part of future improvements to the Encounter Builder/Combat Tracker. The same is true for homebrewing mundane equipment, although I'm not sure items with no mechanical function, such as cloaks, capes, helmets and gauntlets are planned. I guess you could make them as types of armor, though.

Adding on to Davedamon's post - as he stated, once you publish a homebrew creation, you can only create a new version of it. If you are just doing minor modifications to monsters (like changing weapons), you should NOT be publishing them as it's agaisnt the Homebrew publishing rules.