It is not, properly, a horror movie, though there’s horrifying stuff in it.
It’s also kind of the plot of Beau Is Afraid, a demented unraveling of the hero’s journey from Ari Aster, the guy who brought you Hereditary, Midsommar, some stuff you can never forget seeing. I have this recurring dream - a nightmare, really - where I’m trying to go somewhere, I must be there, I simply must, but people keep making me late, and no matter what I do, I can’t make any progress. Proceed at your own risk! Spoilers! Beware!
Warning: Spoilers for Beau Is Afraid follow.