Maybe I'm unusual in this way, but I find myself agreeing with every post that states what they think is wrong, even if it's an issue that I personally have no problem with. Whereas the only posts here that I disagree with are the ones that say "everything is fine".
Because even if it's "fine" - that someone might find an issue with it means that it could be better. I don't know why we should settle for "works if you hit it hard when it rattles" when we could have a smooth-running game.
And I don't think that it's about playstyle. There's a LOT of things that could be improved, IMO, that are playstyle-agnostic.
My list for the OP (some of which just repeats other posts for agreements sake):
Better DMG. Better DMing advice.
More stuff to buy. Better/More interesting ways to spend gold.
Bigger Fonts. Better layouts. Better organized core books.
Better encounter-building rules.
I don't think any of those ought to be all that controversial.
For a deeper dive (stuff that I think could more reasonably argued):
I'd like a skill system that more closely examines the kinds of checks that are actually rolled in the game. Identify the checks that are made and make skills that target those checks. Give each skill more even weight. Does that make sense? I don't expect to be agreed with here, but I'm really quite unhappy with the skill system, in particular how it works in conjunction with tools, but that's another story.
These are all things that I think that people, even if they argue "don't need to be fixed" would come around if they experienced the fixes after they were made.