I'm outside Theta now, really hate the underwater stuff, I was always feel so lost!
From my experience so far (just as I see a lot of people asking about the scares) I really would struggle to call this a horror game, at least in any traditional sense. Thematically it's a sci fi that deals with a lot on the philosophy of the self, and how technology impacts that.
In terms of mechanical gameplay though? No. Not at all. It's not been scary at all. Not even close.
I'm not saying it's necessarily a bad thing, I think I'd be more disappointed if this was just Amnesia again but sci-fi, but if you're going to remove one thing, supplement with something else, and I don't feel they have.