I'm a bit late for this but, a commentary on "horror" and gorn:
I think the failing of horror is actually showing your hand too early and relying on squick or jumpscares for an instant, visceral effect that can't be repeated. Once you see the animated bunch of people-chunks, that's all there is to it. I'd contrast with something like STALKER. Shadow of Chernobyl and Call of Pripyat got the horror atmosphere part down, specifically in and around the lab missions, and some of the mutants (this is why I didn't enjoy Clear Sky as much.. it lacked the lab crawls and focused almost entirely on inter-faction conflicts, which were just guys with guns).
Consider SoC's labs. They're mostly empty, but you're placed in a confined space with nothing but a headlamp and the Zone's echoes of the long-dead for company, until furniture is launched at you from... something...while you're trying to avoid that electrical anomaly. I spent a while trying to find a psi-dog or something similar until I caught the barest hint of a humanoid outline and shot the anomaly (poltergeist), which died. However, it planted a seed of doubt in my mind for the rest of the game. Likewise, the
Brain Scorcher fading your vision to sickly yellow, with that drone in your ears, and the constant hallucinations really set me on edge. Finding out that the entire complex was a massive, hostile brain that I had to essentially cut its life support while dodging the previous victims was intense and disturbing.
The Wish Granter yelling in your mind for the trip through Chernobyl also helped.
In short, elements of the game that remove a normally-present element of competency help heighten tension. Chimeras come at you in the open with no cover or escape. Burers will disarm you and don't need to see you to kill you.
Special award goes to Cataclysm: Dark Days Ahead. Even though it's only text, wandering though a powerless lab with the Mi-go parroting the last words of their victims while obviously not knowing what they are saying still unnerves me. Not knowing the backstory forces you to pay attention to every noise coming from... somewhere... that is obviously inimical/indifferent to human life.
Those don't need jump scares or simple gorn to make the player feel helpless or uneasy. It's a psychological setup instead of a visceral manipulation.