Don't need for this game or other horror games to be "scary" because "scary" to me is such a haphazard term. The Exorcist is one of the greatest horror movies ever made, but is it "scary?" Not really. That however isn't a dig against the movie. It isn't trying to startle you, which is what a lot of people associate with the term. Instead, to me, scary encompasses several different emotions: if I'm creeped out, I relate that to being scared. If I'm bothered, I relate that to being scared. If I'm startled, I usually relate that to something cheap thrown in to get a jolt out of me. Jump scares can be well done, but most of the time it just means that the directors or creative teams are struggling, and take an easy way out.
I have never been under the impression that this game would be scary or terrifying. It always seemed to be going for the surreal and tense moments. What I look for is atmosphere, interesting art, creative ideas, and tension. From what I've seen of the game, it seems to nail these things pretty well. I played Amnesia for 4-5 hours after hearing how scary the game was, and it had zero effect on me. Same for Siren: Blood Curse and several other horror games. P.T. was effective in its unpredictability as it employed narrow corridors and seemingly random instances, but it too was guilty of a few cheap scare moments. So I have no doubt that this game isn't "scary."
But as long as it gets other things right I'm sure it's still a very engaging experience with a great horror-driven atmosphere. That's all I'm really looking for.