I think you misunderstand what people are disappointed about......it's not always WHAT is happening...it's HOW.
It's far from just a matter of people being disappointed that the storyline THEY wanted isn't being followed, it's that the story that is being followed is being done so haphazardly and without skill.
A great example of this is the Jamie vs Euron fight. It was so horribly done it pretty much ruined the episode all by itself because it pulled the viewer right out of the episode because of how clunky it was done. The worst staged scene I've seen on a high budget show that I can remember.
It was basically Euron sitting on a rock, Jamie runs by and Euron says "Hey you, lets fight!"
thousands of sailors were on those ships and just one happens to wash up on the shore, it just happens to be Euron and he just happens to be waiting around when Jamie happens to run by? that's 3rd grade level writing.
No one had a problem with the WHAT..(Jamie fights and kill Euron))...it was the lazy , not even trying writing that pissed people off.
Kind of like the hookups between Jamie and Brienne and Ayra and Gendry in ep 2 (?). Just completely clumsy and thrown in purely to create social media chatter. I mean both those hookups could have been properly motivated and justified but they just decided to skip that part. They probably could have gotten away with one, but throwing 2 in the same episode was just blatantly lazy.
And yes I know there was some slight build up earlier for Jamie and Brienne, but that doesn't excuse the completely throw away way they handled it.
Then we are supposed to have enough of an emotional investment in those relationships that we care when Jamie and Ayra walk out 20 mins later? It ended up just being filler click bait.