There was so much good with this episode but one thing very bad with it too.
The plotting, tactics, political discussion and characters we want to interact teasing their interactions were all really great. Hell even the Grey Worm/Missandei scene which normally I would have scoffed at was actually more emotional than I expected it to be. Arya seeing Nymeria was a poetic moment. Dany confronting Varys was actually quite tense and well written. It was all good stuff, felt like classic Game of Thrones to me.
However the last scene was pretty cliche, predictable, and poorly directed/edited. The effects and visuals were striking and well done, the fire on the ships and choreography was actually really well done. The problem came with the way the scene played out and the way it was edited. It was incredibly predictable, tried to develop a character I have all but lost interest in (Theon), potentially will end up in killing off a character I've grown fond of (Yara), and gave Euron ridiculous plot armor. It was fun, but felt like it could have been done at least somewhat differently to make it feel less forced, maybe have a scene discussing why Euron knew where they were to ambush them, maybe have Euron stay back and join in the aftermath. I'm not sure, but I felt it could have been slightly tweaked and been all the better for it.
I'm still really hoping that Euron's insane luck between knowing their location, having the mists and the winds right where he needed them, etc, is all just a slow roll out of his magic, and they're saving the big reveal of it for some major twist, but I also have zero faith that they're above having it just be really good luck, and that Euron is just 20 good men all in one character.
Having a day to process this one has kind of soured me on it. The battle was impressive production-wise, with the ships and fires and all the extras, but it was a mess of rapid cuts, other than the very good final lingering shot of Silence sailing off. It almost felt self-aware that killing off some Sand Snakes would earn it some plaudits from fans, which, when you're trying to boost engagement by killing off characters you fucked up so badly that fans want them gone, you're in a bad place. (Also, man, I feel bad for those actresses, because having now seen those characters to completion, I think it's pretty safe to say that there was not a single scene written for them that would have allowed them to sell those characters, and so they got assigned really brutal deaths to get everyone out of the mess they were in)
Sam's stuff is a poorly thought out deus ex machina, as is Qyburn's ballista. Olenna/Dany and Jaime/Randyll were decent scenes, but all of the other monarchs-holding-court stuff was fairly uninspired retreads of stuff we've already seen. I will say giving Olenna some of the "be a dragon" stuff from Dany's book hallucinations was good, especially if her early defeats here in this episode are going to push her to go more all out.
I'll give them the benefit of the doubt for now on the Nymeria scene, and assume that's set-up for something later, because otherwise it managed to use the weight of a season 1 callback to stir up some emotions, but otherwise was pretty weak, and needed the after-the-episode interview to explain what they were even really going for with it.
I guess the big thing is they seem to mostly be riding their budget and the impact of things that have been set up for years to carry the show now, rather than any interesting writing or character development. And, I mean, it's possible that this story just really has an uninteresting end game, and that everything has been so heavily foreshadowed and set-up that the end is going to feel kind of static if you've been paying attention, but it's also possible that they just don't have a good feel for how to progress these characters anymore without the book to guide them.
Also, this episode just didn't have a scene the quality of episode 1's Hound stuff to carry it. The Hound is the one character who really still feels dynamic right now.