I'm not one of the book readers but I'm guessing that without the benefit of some meticulously plotted source material to draw from the wheels are in real danger of falling off.
Also, they've boxed themselves into a corner with so many story arcs that just aren't interesting or have been exhausted to the point of not caring any more
- Arya still in training but now blind training. Whoopee doo.
- Danerys still no closer to going to Westeros. I assume she'll eventually win over the Dothraki and have them join her army. But it's a chore to watch and feels like something we've already seen.
- Sansa, Theon, Brienne, Pod. More travelling I'm guessing.
- The Dorne/Sandsnakes stuff. Literally the worst thing about the show in terms of dialogue, acting, relevance to the main story (everything).
The only remotely interesting plot lines for me at the moment are the stuff at The Wall and the power struggle at Kings Landing. Also I really think they need to have more than 1 episode with the WhiteWalkers this season. And likewise I hope they don't just ignore the dragons until they need to blow all their budget on one episode. We get teased with these every season which is fine when you have other interesting characters and subplots to follow but I don't think this is the case any more. I think there needs to be some semblance of an end game building or it will fizzle out.