I think you guys are being a bit harsh. I think the acting was fine and the cinematography, music, and CGI were all excellent. The plot was a bit silly at times, but some of that has to do with the source material and some of it was the writers taking their own liberties.
The season was mostly let down by it's pacing and script, I think. I'm not sure how much I can say here without getting into the details of the book, but I'll say that its obvious they're trying to draw things out as much as possible but don't seem to know what to do with these characters in all of this downtime.
Also, I didn't think that last scene with Alicent or Rhaenyra was out of character. Rhaenyra want's Aegons head because she thinks its the only way to end the war without the constant threat of a larger scale civil war, which is what she has wanted throughout the series. She may have been willing to spare him earlier, but it's harder to do that now that Aegon has mustered enough support to start sacking castles and burning towns. It isn't clear if Alicient actually agreed to sacrifice Aegon, but she has grown increasingly horrified by her children's actions throughout the season and probably realizes that they're going to die anyways so might as well save what she can.