It's funny, I used to find the dialogues amazing, but now I've been re-watching the show with a critical eye, I find them cheesy as fuck.
I think there’s just been a steady decline, because each season has used less and less book dialogue. It’s not a coincidence that the best scenes are the ones that basically treat Martin’s work like a script (I’m thinking, for instance, of the scene in the S3 finale where Tywin puts Joffrey to bed).
Then this season they seemed to be playing a game called “let’s go out of our way to not use book dialogue, except where it makes NO sense” (Ramsay’s ‘a feast for the crows’ springs to mind).
There’s a reason that the conversation between Dany and Tyrion, a meeting that they were so desperate to have that they contorted the narrative into a pretzel to see through, had no significance and was incredibly boring.
Also @theculturalvacuum and I pointed this out in the Carol’s Landing Retrospective, but a lot of the dialogue just doesn’t follow any rules of conversational pragmatics. It’s like two people just saying things near each other, but their lines aren’t actually logically following from what the other one says.
It’s just bad writing; there’s no other word for it.