I think people underestimate the quality generally on display. The 'look' of the show is absolutely incredible, from sets, cg, costumes and so forth. It's like a huge-budget film, every episode. That side of things is amazing imo.
With notable exceptions, the acting is also brilliant. I think Alicent/Rhaenyra are doing superb work, as are the vast majority of side characters.
The biggest miss is the writing, which is just infuriating inconsistent. Sometimes it's genuinely good. But then it can also be incredibly stupid, and the contrast is what I think gets people so riled. Like the Cole discussion in the finale - it's actually really well written, shot and acted. But it makes no sense, leads to nothing and is randomly placed in the episode/season. Or this whole Lannister finds a pirate sub-plot. We didn't need that. If a bunch of (cg) ships had shown up next season and they'd had a throwaway line like 'turns out you can buy anything with Lannister gold' in the small council, the audience would be happy. Instead this jarring, long part of the season finale is spent in Legend-of-Hercules levels of schlock. It's just weird.
As everyone is saying, it screams of HBO need 4 seasons, sttrreeeeetttccchhh it out