I wasn't saying that dialogue was bad, but 20 mins of raw dialogue where the conversation just meanders and nothing really happens, becomes tedious. And when you have two or three 20 minute long scenes like that, the film becomes a chore to sit through.
I like Aaron Sorkin, his films are mainly people talking in rooms, but he seems to have found the perfect balance between having clever, funny dialogue, and having something actually happen. So whilst his films are dialogue drive and a good 90% of every film is dialogue, it doesn't feel like it because there's always something going on (or it always feels like something is going on, even though it isn't necessarily). Also, he caps his conversations at 5 mins and they're still as effective and funny as anything I've head from Tarantino...
Having excellent dialogue is good, it's essential but it needs something to break it up. It is possible to have films that rely too heavily on dialogue.