Loved every bit of it.
For the people not liking it, you really didn't pay attention to the details of the movie. It has tried portraying many things from a single thing.
Psychological horror is probably the best kind of horror, where you do not need a specific physical entity to be afraid of it.
It will always find a way to scare you by merely showing anything.
Overall, Oscar-worthy movie, not even lying.
Outstanding production, acting and writing.