Feminism in general is politically incorrect. Only certain kinds of feminism are acceptable and Wonder Woman doesn't fit into any of them. Wonder Woman refusing to kill can work but Wonder Woman as a pacifist makes her superhero movie a non-starter.
And the magic/mythology thing is really hard to work with. I don't know why Thor managed to do such good box office but I do understand why a mediocre screenwriter couldn't really write him into The Avengers.
Uncomfortable cultural politics, clumsy backstory, and yes, a fear that the unwashed don't accept women action heroes, these fears are undoubtedly part of the slowness to pursue the comic book movie gold mine.
But honestly there's a good chance the generally poor economic environment plays a major role in caution.
The best solution of course is to have James Cameron do the WW movie.