Eh, this is one of those unanswerable questions. Because with 20/20 hindsight, people can always say ... "Well, sure, it worked in practice, but imagine how much better it would have worked in theory!"
That doesn't mean 5e is perfect, but it is interesting that people say it could have been so much better, with "better" always meaning, "Designed to more closely match my own gaming preferences."
I think that what most people forget is that design involves a lot of tradeoffs. Added complexity (and classes and "design space") might mean that the game is less accessible to certain people. More importantly, features that some people love (to make it "more like" 1e, or 2e, or 3e, or 4e) would not be popular with people playing today.
In other words, I agree that things can be better (not right). But the majority of people I see criticizing 5e are not making the critiques from the point of view as to what would make it an even-more broadly popular product, but instead, what works for them.
I mean, I love stick shifts. I think cars should have them. I buy cars with them. I always advocate for them. But my niche desire would not be appropriate for a broadly popular car.