“Horror” is easy. Dim lighting, spooky creature, feelings of powerlessness(such as limited view, limited to no combat capabilities, restrictions like a stamina meter, the like).
GOOD horror is hard. Good horror is the kind that sticks around with you, leaves you feeling uneasy even after the end. That takes talent, creativity, and genuinely, a bit of bravery. It takes understanding what makes us feel afraid. Facing your own fears, making them a reality, distorting that reality into how it makes you feel.
Silent Hill, at least the first three, are exemplary for this, in my opinion. They explore the fear, but also the sadness, the anger, the confusion. Everything fear brings with it. It molds itself around the characters, letting us experience those emotions as they do. They can be genuinely visually unsettling, then swing the psychological side of things right at you.
Hell, you can even have that and hit a bit of a power fantasy. Call of Cthulhu: Dark Corners of the Earth manages to have early moments where the tension keeps rising because you are basically powerless to stand and fight, to manning the guns later on.
Not everyone has the spark for good horror. It’s not a bad thing, just means it’s not your strength.