Fourth Edition D&D takes away a large amount of character customisation that 3.5 allowed. It unified powers and spells in a way that I do legitimately believe diminished the flavour difference between casters and non-casters. It flattened the power curve and produced fewer outliers, fewer opportunities for players to be outrageously good. It took flexibility from the Dungeon Master and gave them instead larger sets of pre-fab mechanics.
All of these things are true, and legitimate concerns against 4th Edition D&D.
Everything 4th Ed did was (reasonably) holistically sound. The flattening of power was intentional. The simplification of character building was intentional. The importance of formula and structure to the math of balancing the game was very intentional.
Of games where the storyteller or dungeonmaster or whatever you want to call them has to do a large amount of work, 4th Ed D&D was the first game I played where they tried to make that role approachable. The DM’s role has numerous tools to make play expression simpler and gets out of the way of things that aren’t explicitly handled by mechanics. In the end, 4th Ed D&D was about making it easier for someone who had never run a game to say to their friends, ‘Hey, I have an idea-‘ and to go from that to running the game. The deliberate segregation of pure flavour and pure mechanics meant players who wanted to reskin their characters’ actions had the option to do so. Not everything worked, but it still was trying.
I get there are a lot of reasons to dislike 4th Ed, that’s fine. But it’s approachable, it tries to be balanced, and its tools for storytellers are way stronger and way more inclusive than people seem to want to give it credit.