This is an anime that comes once in a generation. It is not for everyone. Just like Nolan's movies, this anime is on another league. It takes a lot of efforts for the viewer to understand a single episode. People who are rating it low, either can't get it all or too dumb to understand the underlying meaning.
Watch it carefully and slowly. Welcome to the world of imaginative roller coaster, where you will forget certain things and slowly understand what is happening. There are situations where you need to wait 5 or 6 episodes to make out the complete meaning of a scene of episode 1 or 2! As I have expressed earlier, it is not for average joes. There are inter dimensional hypothesis, theory of relativity and lots and lots of fictional concepts.
Enjoy slowly, one episode per one day/2 day.
This type of anime is really really really rare.