I 100% think that having simple "I hit it" classes like the Knight and Scout and "I burn it" classes like the Elementalist was a huge improvement to the game. More variety in a class based game is good.I don't think you necessarily do have to do it.
The monster math certainly did need changed. That was good.
In my opinion, the changes to how to approach the game went in the opposite direction than they should have, it it lead to a weird gameplay feel in which parts of the game felt like they were working toward being different games (on top of already being a very different game from what came before). That created a bit of disconnect for the group I played with at the time.
4E started with a lot of good ideas. The execution of the ideas needed changed, not the ideas themselves.