I only sort of agree with this review ( it’s as valid as any other I’ve read). I had a completely different theory, though.
You forgot to mention one thing. There are parents in the movie, but only Moms. There are no fathers in any of these kids daily lives. I think Jay’s father is dead, and Greg briefly mentions his father. Paul and Yara’s parents are never seen or spoken of. Jay interacts briefly with her Mom at the end of the movie.
I think the meaning of the movie is in all the tiny details. The details of the kid’s conversations, shots of photos,Yara’s book excerpts, the forms that It takes, and lots of emphasis on water, mirrors, and windows. For example, Jay’s mother is an alcoholic, as she’s almost never seen without a bottle of liquor in the shot with her. (I think she drinks because her husband is dead.)
As for the old man on the roof, I believe It was trying to find some other way into the house, since its first attempt failed, and I also think the naked old man is the image of Jay’s grandfather. There are brief shots of photos of Jay with various family members, and he’s in one of them.