Nobody is going to be happy about one thing. It is impossible for everyone to agree on one thing. Complaining is what people do, so you can't say fans are picky because even if the fans who are complaining got what they want there still will be someone complaining.
Especially when there is some source material involved then people become specific especially if they like the source material. Lets see, Lord of the Rings, Spider-Man, Batman, James Bond, Star Wars etc, etc, etc. So people will always complain.
So expecting for everyone to be behind this movie would be just as foolish as condemning it before we have seen the final product. However you still should be able to make an assessment of what the movie will be like fromt he stills, production value, casting etc etc.