but all these sorts of things would require new animations for all of the characters and then at that point, why not just make a bunch of characters.
This is not how game design works at all.
The idea of customization to an existing character is class is to model around the existing strengths and weaknesses to have functionality suited for the player. Even something as early as Dungeons of Dragons, you could have a Cleric focused around so many things, but in the end they are still at their core.
Do not overstate the effort required. A new character is a world's of difference. Sure, something like graphics and audio are not much for a programmer's work. But stuff like the rig, the normals, the thousands of variables that dictate stuff like pushbox, hurtboxes, weight, ledge perimeters, etc... Stuff like that is completely different realm of work compared to making a new character, something that takes valuable time from the programmers and designers.
Let alone that is disregarding the core game design philosophy that is character design. You don't make a character to have moves for them. You make the moves for the characters. An additional level of variety of moves themed to compliment the core design philosophy can fulfill the character's design and drastically change how they play, but at their core they still obey their designated design rules.
Not like I am disregarding the rest of your post that said more variety would be nice, but the statement is still well off.
This is also why even if the game had another year of development, a lot of the community's so-called "must haves" will never happen. The reason why Ridley hasn't happened is because none of their designs have been satisfactory for a playable character. People can spit out movesets and ideas all they want, but they'll never know how hard a developer has tried to make something work.