I'm not really into slow horror movies. But obviously this one has to feel slow to help you understand the isolation and the super slow decent into madness. I think this is one of those movies you have to see at least once in your life.
I use to think 5 months in a giant hotel sounded like a vacation. I've now changed my mind about that since being in quarantine. I think I've only seen this movie once before. It's still just as boring.