I actually liked 4E well enough for the reasons you said. I think the latter period design in 3.5 was excellent, and they did a good job exploring that (even with the sometimes weird MMORPG-ification of the system). I had a lot of great sessions with 4, and it gets more hate than it deserves; 5E was a step down in every way.

I agree with you on the "GMs shouldn't have to redesign" point for sure, but that never seemed to be the problem to me. 3.5 got crazy unbalanced because of the diversity of builds and source books. If you wanted a grounded campaign, you just limited the players to core books (or maybe core books plus a few others). The craziness really came from dips, and combining stuff from totally different books that was never intended to be combined.

Finding that stuff was fucking fun though, and in a group where everyone knew the system backwards and forwards, could result in some really awesome and very different characters. I once did a level 20 gestalt campaign with every source book allowed, and holy shit was that some bonkers fun. Everything in 5E just feels the same, which cuts off a whole dimension of enjoyment from the game for me.