I, one million percent, do not agree that the second season was worse than the first.
I agree that there were changes that made the show different from the books, but I would argue that the changes made were largely necessary ones that serve the needs of the different medium.
TV and books are very different things, with different pacing and narrative requirements. You can see how badly some films do at adapting written texts when they are slavishly loyal to the text rather than being aware that an adaptation is a distinct beast.
The second season was narratively stronger than the first, it was better TV, in my opinion, because some things were altered for pacing and fluency problems. Also, Blackwater was one of the best episodes of television I've ever seen.