It's difficult to give a good critique of this movie given it's unique style and the time it came out in. The movie uses psychological horror in the form of a found footage film, found footage which was uncommon, in fact, unheard of when the movie was released. People believed this film was real for a long time.
The movie is simple in it's style and is really unique and it's part of the reason it gained such high praise. I enjoyed the movie, but not everyone will. That's how art goes.