I had heard good things about the film, and how important it was to go into the film knowing as little as possible on it. I must be on a completely different wavelength from those people, because I think it's one of the dullest horror films I've ever watched.
Building up tension is one thing. But I say, without exaggeration, that most of the movie is the main characters blindly groping around in the dark. Long stretches of the movie consist of absolutely nothing happening. The characters are underdeveloped even by the usual standards of horror movies, neither of them being given identifiable traits.
As for the shocking twist...I'm chalking this up to Older Than They Think
, because evil children are nothing new. Not only that, but we get absolutely no explanation for why they're doing what they do. Sometimes a lack of a motive can be scary, but in this movie's case it ends up making the whole thing feel nonsensical and a waste of time.
I know it's not a good idea to try to speak for everyone, but I do genuinely wonder how much appeal this film could have for experienced horror fans. It's a film in which very little happens, so unless you've got a very active imagination filling in possibilities for you, I wouldn't recommend it.