I really think that, if Sinister and Anabelle are the types of horror movies you enjoy, there's a lot out there for you to see. For those of us who don't, films like It Follows get hyped because, well, it really IS the best horror flick we've seen in years - just cuz all the other are more of the same!
Having read your various responses, I can say the disagreement boils down to this: Much of what you consider a failing in this horror movie, I consider an improvement over mainstream horror films. Your suggestions for this film would, for me, ruin it. Also, some of the "mistakes" you claim this film makes were actually 100% planned decisions.
the lack of an explanation
Too much explanation is my #1 gripe with mainstream horror, hands down. Detailed back-stories and overcooked motives for what should be vague, forboding monsters (I'm looking at you Freddy/Michael remakes). Huge lists of rules that ghosts/haunted objects have to follow. Trying too hard to make something realistic A) only draws further attention to how outlandish a concept it is and B) sucks away the terror of the unexplained. A terror with no known motives or rules is scarier than one with, every time.
made me think the movie was going to end in some sort of Machinist-esque
Gratuitous twist-endings, particularly of the "It was the same person the whole time!" variety are a dime a dozen, and are one of the go-to solutions for "shit, how do we end it?" syndrome. I would rather It Follows cut to credits 10 minutes early than have an ending like this tacked on.
I was really hoping for something that made me think of a skinwalker/nlaadalooshi
Once again, a huge over-used cliche that would have, for me, ruined the film. "Turns out it's an ancient this-or-that!" is SO tired and overdone. Again, a 10-minute early cut to credits would be preferable than this.
The whole changing back and forth between gaps of technology
This was a very intentional decision. That clam-shell reader thing? Doesn't exist, never has. Then they show the character talking on a phone with a chord in the next scene. The director wanted to create a nightmarish quality, set in a jarring ambiguous time period that just doesn't quite feel right.
You'd think her parents would've been concerned or that it'd at least show a scene with them to add to the story
100% intentional. Not only do you never see the parents, but the entire neighborhood is mysteriously underpopulated. This adds to the isolation and fever-dream quality. The kids are eternally on their own. An explanation of "Hey guys, the reason the parents aren't there is cuz-" would just feel forced, and insulting to an audience. I don't need my movies spoon-feeding me answers to every "what if?" scenario. Immersion is not "how realistic is it?", as much as how strong of an experience does this create?