My problem with season 4 as a whole wasn't the ending - I actually really liked the ending. But honestly, if the anime just stopped at season 3, I would have been satisfied. My issue mainly comes down to how much of a slog it is to watch eren and zeke try to kill eachother for like 9 episodes straight with large battles that got over-focused on "giant monekey fighting funny pointy ear giant!", when honestly the non-titan combat was more interesting. It was just a slog to get through. The first 3 seasons at least had something you could look back to that at first seemed insignificant but meant something later on, this just... didn't.
BUT... there were pretty solid moments in this season. I think nearing the final 2 episodes it really began to pick up again and we got to see some really well thought out stuff occur.