You have pretty much the same opinion as me.
Season 1-4 are pretty flawless. Season 5 is pretty boring, slow and awful. Season 6 is an improvement, but still pretty flawed. Season 7 was, perhaps, even worse than Season 5.
Even then some of the good parts from Seasons 6 and 7 are so good because of things that happened before that were bad
like Cersei blowing up the Sept is so great because she killed off that terrible, boring plot line with terrible, boring characters like the High Sparrow and Tommen. The only good thing about Tommen's character is his cat Ser Pounce, let's be honest. I would normally never root for Cersei, especially as a book reader, but I just couldn't help cheering when she succeeded, the High Sparrow was that bad.
Similarly Euron's boat attack is so good because he kills off the Sand Snakes which was so satisfying because they were such awful, annoying characters. Again I found myself rooting for a villain, the Sand Snakes were originally intended to be protagonists, wanting to avenge the death of their father, a fan favourite whose death was absolutely soul destroying, but because they were butchered so badly and so annoying, I wanted Euron to kill them for Cersei.