There’s two ends of the horror spectrum
*puts on my little cinema/writing degree hat*
This is because Gothic horror is about repetition - cycles that repeat endlessly with no apparent end. Of course the mansion is cursed - how else can you explain the mundanity turned to insanity? How else can your heroine become more and more desperate for an escape to the endless madness? (Now, some Gothic horror - especially Southern Gothic horror - dispenses with the supernatural metaphor and just plainly makes the casual cruelty of society and the family the cyclical antagonist + creeping dread).
Versus eldritch horror, which is about the unknown, literally. We can't describe it because we can't comprehend it, and even trying might lead to madness. The mind will produce something far more fearsome if given mere tidbits of information, only hints as to something horrible and indomitable, than if you describe every intricate detail of the horror's maw/tentacles/butt/whatever.
They're different ends of the "horrors of the mind + metaphors about humanity" spectrum and I just think that's neat!
