i totally agree. i loved age of ultron, and particularly enjoyed ultron himself.
he was extremely cool looking. from the mark 1 to ultimate ultron. all of them looked great. ultron mark 1 was just creepy, it was a great introduction to the character. prime is awesome, to me that look IS ultron. and ultimate ultron was bad ass and looked like he beefed up for battle.
i'm not sure what else people wanted out of the movie. i feel it did a solid job at continuing and building upon the rift between steve and tony. it fleshed out some of the characters a bit more, we learned more about the relationships between the team, and it fed the larger picture.
part of me thinks that, for some people, the movie was never going to live up to expectations. the first avengers movie was great because there wasn't really anything like it. heroes with their own franchises coming together for a movie. age of ultron was never going to live up to that. also, i think some people are just looking more towards infinity wars since that'll come closer to giving people the feeling they had for the first avengers movie.
i don't think civil war is going to suffer from this though because it's going to be hero vs hero.
but hey, i'm someone who enjoyed iron man 2, iron man 3, and the dark world.. so what do i know?