I get that. And I feel like the critic when it comes to Jennifer Lawrences acting is also valid.
But it is supposed to be a parallel universe with the main idea that Mystique NOT becoming a villain will change the time-line for the better. So, Mystique being out-of-character so to say, is the entire premise of her storyline in the second trilogy...I don't mind it. She is still very much antagonistic to Xavier in many movies and a radical mutant rights advocate. I think that makes her not too different from some versions of her comicbook character (but painfully missing Destiny!). I never was a fan of backstabbing Mystique who is evil and crazy for the sake of being evil in the comicbooks and really like the comicbook plot where it was explained that Mystique's powers influenced her mental health and Psylocke saved her from this condition.