The weird thing is that, in my experience, most of the people who say that about Adaptation seem to understand why the third act functions the way it does, yet they seem to not like it for the exact reason they appreciate it doing what it's doing.
Charlie and the Chocolate Factory is a perfectly acceptable, surprisingly faithful adaptation until the trainwreck that is Wonka's mawkish subplot, which drags out for twenty minutes after the movie is, for all practical intents and purposes, OVER. And I'm sorry, but in Roald Dahl stories parents are not to be tearfully reconciled with. They get eaten by rhinoceroses.
They Might Be Giants has a lovely, unique tone, supported by brilliant acting... until we end up in that supermarket.