Why is everyone surprised and why are some acting like this is bad?
This is a part 1. Some people (and especially critics) are annoyed because:
1. This is basically a bridge to get to part 2.
2. There's no games and it's more of a political drama.
3. It's significantly different from the first two films.
PLUS the critics scores are lower and Mockingjay is widely considered the weakest novel of the three. So it's not a huge shock that some people might have stayed away and will return for part 2, which will undoubtably be massive and maybe even the biggest of the franchise. Let's not act new.