Let's start this off by saying, I liked the first two. The first one was ROUGH, and showed off its low budget and humbleness. Second one was great, was striking that perfect balance of shock, gore, and comedy. Third one... Too much shock, for shock sake, and not as much comedy.
The major issue here is weirdly too much backstory and "LORE", they're trying to add rules and logic to everything, while also being cheeky fun. The lore is convoluted and confusing. You can't be like; eh don't think too much about it, and then dedicate a quarter of this film to the logic behind the Art Demon.
Then there's the "SHOCK VALUE" of this one which was more TEENAGE REBELLION than genuine shock. "Isn't it crazy the melted face lady is masturbating with a shard of glass?" "Am I pushing your buttons Christians with this ham-fisted blasphemous JESUS symbolism?" Eh, just lost the tastefulness and subtly. There was shock, in the other two, for sure, but it was never so juvenile and basic.
Everything else was fine, not great. The gore was way better, they remembered humans have layers inside of them, and you don't see as much hollow cavities with really floppy and rubbery shells like in the first two.
If you missed it in theaters, not that big of a deal.