Event Horizon does just the right amount of showing you the horrific monster style stuff while also leaning almost completely on the "people are the real monsters".
That's fair, it is a bit tough. I really liked Hereditary, and Midsommer to a lesser extent. Then I watched a "complete guide" by Novum (YouTube). It's literally 6:55:24, but I watched it over about a week while working. It definitely made me appreciate it even more.
Don't know if it would help you watch it, but it was very interesting (although it dissects the whole movie, so it's just a giant spoiler).
The Hereditary one is "only" 4.5 hours, but also worth watching if you liked Hereditary.
You should. Hard to get through (the runtime) but very interesting. I knew there was a lot of thought that went into it, but had no clue there was that much lore and real-world comparisons.