All style, no substance
I love Ari Aster's second and third movies but this one always struck me as boring and plotless. It's nothing but really well-framed symmetrical shots of theoretically spooky stuff, and, yes, this film LOOKS very good. It probably could've earned Oscar noms for its cinematography or production design. But the script is so superficial.
Yes, the decapitated child head is unpleasant to look at, especially when covered in ants and flies. And? Obviously, nobody wants to see that, so it's by default scary. But does it mean anything? That's the whole film for me. "Wow, look how scary that image is!" Okay, but what does it actually mean? Oh, nothing. If I made a horror film consisting solely of gore and dead bodies, would that make it scary? As a filmmaker, I didn't even try to say or do anything, I just laid dead bodies in front of the camera for 90 minutes and thought little of a story.
Most classic horror films like The Exorcist, The Shining, The Thing, Halloween, Alien, even older stuff like The Haunting and Psycho understand that the imagery is only an aid to a great script. For example; the maze in The Shining is terrifying but would it be terrifying without the context of the story? Probably not. Glad Aster figured it out with his later films.