Overall, I loved the episode and am loving this season.
A couple legit gripes, but a lot of the complaints I see are just silly.
Blackfish dying off screen is a legit gripe. They brought him back after 2 seasons. Reminded usv how G'd up he was. They def should've showed us how he died. That was an error.
The Waif/Arya ending is a legit gripe, tho not an error imo. From a fan perspective, they've been building up this confrontation for two seasons, we wanted to see an epic 1-on-1 fight sequence. However, I don't think it was an error because the Waif was genuinely a better fighter. In a fair one, she's gonna beat even a healthy Arya. A wounded Arya stands no chance. It made much more sense for Arya to lure her into darkness where she holds the upper hand. It was a great illustration of how her training paid off.
Most of the other complaints I'm reading are shyt. People wondering what was the point of Arya in Bravos
Clearly she just morphed into a master killer. Sure, the Waif was giving her that work, but most other foes don't stand a chance. She went from a weak little girl who only knew how to "stick 'em with the pointy end" to Arya Bourne! And now she's headed home!
People complaining that there was no point to Riverrun
That was big for the storyline. It got Jamie out of King's Landing, and resolved a major L for Sansa: they're not getting any help from the Tully forces. People seem disappointed there was no battle, well there was never going to be a battle of Riverrun, that was a siege. One that would've lasted 2 years if they went that route.
People complaining that King's Landing storyline doesn't matter
The very first scene of the series showed us that shyt was getting crazy beyond the wall, yet King's Landing has been a major outline and shyt that happens there has affected things at Castle Black. Just cuz you can't see how it will unfold, doesn't mean it doesn't matter, just sit back and enjoy the show. I get that people hate the High Sparrow, his soliloquies were getting dreadful, but hasn't had one in a minute. And it's undeniable he's playing the game with the skill of prime Bobby Fisher. Cersei showed her cards, and he pulled trump like a boss