I wouldn't be too concerned about MoS. The average rating is still good, and the negatives are odd, because some of them are rated 3/5 and B-, ratings that would normally be positive. I think it's also suffering from a backlash against Nolan (claims of it being too "serious," too much like Batman begins, and Cavill never smiling as Superman like Christopher Reeve did (seriously, one review said this)), and some critics' dislike of Snyder because he is a visceral/spectacle filmmaker, and favors the image over the "story."
The negatives so far that I can see are it doesn't have enough character development (can we get rid of this critique already? It's such a meaningless thing to say), and the final action scene is "too loud" (lol)/goes on too long (this didn't seem to bother them in Avengers), and uses too many experimental camera techniques (how is this a negative?). So in summary it sounds like Snyder and company took some risks, and critics are mad that they didn't have Supes throwing out a quip every two seconds to "lighten the mood."
