So I just watched "It follows" [May contain spoilers]

So, after someone introduced me to this film, on one of my giveaways, I was eager to watch it. Finally I found a good version, with korean subtitles, but it was better than watchable. I was reading a few critics, and someone wrote, that after 10 minutes he had to turn on the lights, I was excited to watch this movie. But after finishing it, I felt that it was a complete waste of time. I'm not gonna lie, but for me, the whole movie was about the girl (Jay), and her friends, running away from the thing, which was chasing Jay. I was expecting, that they will find out IT's origin, or at least a few info about it. For me, it wasn't scary either. Hell what should be scary if IT's just a walking human with blackened eyes? So for me it was a pretty mediocre movie, which had a lot of tension, but failed to use it up, like The Blair Witch project did. Do you think the same, or was there a hidden literary depth, which I missed? Because in "The Babadook" there was a more deep meaning, which I understood only after watching the film, but here I couldn't find such thing, only a few porn scenes.