This is one movie where the critics knew that Man of Steel was going to be quite different from the Donner universe but still couldn't quite handle the departure from the Donner films into something so completely different that MoS was. The critics were expecting something at least similar to the Donner films and Snyder/Nolan never intended to give them that. Hence the low rating.
Part of the reason why Man of Steel was like this is they listened to the fanboys who drive the comic book genre who supremely hated Superman Returns and acted accordingly by realizing that a different, new and fresh take on Supes was in order. Without fanboys, the comic book genre wouldn't exist or just be barely on life support.
This post was edited on 8/22 at 5:58 pm