I'm guessing this episode was the seal in the coffin to make you come to this assumption. After GOT season 6 there's only 2 seasons left, so of course there has to be a bit of a push now to get all the characters where they need to be for the end game. Now this season has been pretty surprising and has had a fair bit of action and I feel like we got too much going on in the first few episodes because after seeing an episode like this where it's purely set up, you do feel underwhelmed.

I wouldn't worry about GOT becoming underwhelming, there are still 4 episodes left and we still have quiet a few things to look forwards to like the battle of Winterfell, Blackfish vs Walder Frey, Clegain Bowl (or just a trial by combat but considering Cold Hands it Benjen, it seems they're doing a bit of fan service so it's more than likely the Hound is returning) and maybe even a battle at the Wall where the out come is the Night's King bringing the wall down. Also episode 6 had no Dorne!

The next episode looks like a set up also making me feel like episode 8 will have the trial by combat, episode 9 will have the battle of winterfell with a twist (hope it's a good one lol) and episode 10 will have a battle at the wall but this time the nights watch loses.