The 3 things actually wrong with WoW:
1) Overly complex slot-machine rotations, with too many action bar buttons. It's one thing to have a bunch of utility abilities filling your action bars, that's okay, but having to hit 14 different flashy light-up buttons just to do damage is retarded. If an ability exists solely to fill up GCD holes in the rotation, and isn't actually fun or meaningful to press on its own, just delete it and bake it into the autoattacks. The whole "nobody wants a dead second in their rotation" concept is fucking nonsense. It's okay to give people a second to scratch their nose during an 8 minute boss encounter.
2) Over-reliance on mods to communicate necessary and meaningful information to the player.
3) Borrowed power. At the very least, take some of the signature abilities from an expac and turn them into a row of talents, something to remind the player "oh, right, I was there" or bake some of the key passives into the class. After BFA they took two of the key Azerite traits for DH, Furious Gaze and Chaotic Transformation, and baked them into the class as high level passives.
And for fuck's sake, let people have mining and gathering for free. Making gathering professions exclusive to crafting professions just leads to a situation where the overworld is less fun for everyone, and makes the economic inputs largely dependent on farming bots. If Korthia has shown anything, it's that it's fun to pickup nodes and chests while questing. That's a fundamentally important gameplay loop to the overworld gameplay of an MMO.