Following a MOBA model of class design (a small suite of scaling bespoke powers available at the beginning of play, upgrades and new powers available via item acquistion, a high level capstone) is unironically a good idea.
For myself, if I want a game that does all things I want in a ttrpg and lets me ignore stuff I don't care about, the ideal rpg is PathFinder 2e.
But as I think about the people I play with, I feel like, for a lot of them, it might be better to take a few steps in the opposite direction: have character with impact race and background, a class built around a single mechanic that comes online pretty early, and then let the character proceed form there not by class tables or level-based bonuses, but in-universe rewards. This allows the game (the story, the fiction) to guide progression.
This is because I find a lot of people don't think of dnd as a game, really. It's a shared story thing, with gamey stuff tacked on. They want to write characters and tell stories about those characters. Maybe roll some dice. They don't want to do "builds" or master systems. They don't care for the wargaming roots of the hobby, but aren't quite willing to go full improv.
The structure would be something like: you should have all your core/ key/ defining features at level 1, though perhaps in limited versions. By level 5 or so you should get all the basic stuff up and running. Past that, rewards should have direct in-universe causes: you learn spells by finding scrolls and books, you learn maneuvers and feats from... scrolls and books and maybe trainers. (Skill feats would be the rogue-group option.) You get boons from spirits, and magic items to expand and enhance your capabilities.
The decisions you make past level 1 should only be specializing in stuff you could already do at level 1 - ie Fighting Styles. They should not add new options (ie spells at level 3) or change the priority of ability scores.
But level 10 or 11, you stop getting major number improvements: your base attack bonus has peaked, you only get a couple hp per level, no more spell slots, etc. It's all about paragon and epic boons and magic items by then.
Cons to this approach: 20 classes is probably a minimum. (Not as big a deal since classes don't require subclasses or as much mechanics). Races will be less flexible than the current system (though probably not as much as, say, PF2) You
absolutely must give dm's solid, understandable guidance on how many rewards to include. (Bad: no guidance. Okay: you must give X items to players at level Y. Great: here's some different rates for rewards you can give, and how those affect the game as a whole.)
