It Follows. The film actually is a social commentary. It's set in the greater Detroit area, and the main characters are the teen aged children of the well off who live in Grosse Pointe. They live indolent and aimless lives full of afternoons by the swimming pool and summertime hook ups in the backseats of BMWs. They're the kids who live North of Eight Mile road, whose parents have beach cottages on Lake Michigan and whose high schools have Olympic sized swimming pools. When one of them is infected with a supernatural STD, somehow the guy who passed it on knows all the rules and spills the beans complete with demonstration. Of course the rule is that, if you have IT a supernatural invulnerable entity invisible to everyone but you willl relentlessly stalk you until it kills you, but the good news is you can pass it on to someone else by having sex with them and then you're safe until the IT in IT Follows kills that person, and guess what, you are once again the target of IT. Thus, It represents something new for the fortunate sons and daughters, the need to continuously watch your back--a condition both novel and horrific in this strata of society.
When the kids come to grips with that reality, they decide to pass IT to one of the nerd (incel) boys (kind of hilarious) who had the hots for the infected girl since Middle School. He then promptly goes south of Eight Mile Road, to have sex with and pass it on to an African American streetwalker. Presumably nerd boy didn't give his unsuspecting victim the warning Grosse Pointe girl received, leaving this condition to infect and spread throughout that community. Kind of a genocidal dick move, when you think about it.
And that's how the movie ends--with the Princess and the Nerd walking down the sidewalk in their comfortable Grosse Pointe neighborhood, always watching their backs to see whether IT is following. Serves them right.