Everyone is playing true to age. There are no 40 year olds playing teenagers in this movie, just a bunch of people in their early 20s playing characters roughly the same age.
It's a slow burn with a substantial on screen body count. There's lots of atmospheric stalking and misdirect-style character building, interspersed with people getting axed to the head.
[Spoilers, skip the rest of this write-up if you've not seen the movie.]
It's kind of the horror movie version of an old joke. There's an old joke that goes something like this: A father and son are in a car crash. The father is killed instantly but the son is rushed to the hospital for emergency surgery. As the boy is wheeled into the operating room, the surgeon exclaims, “I can’t operate—that boy is my son!” The punch line? The surgeon is the boy's mother. Lots of people break themselves in half trying to figure that simple joke out, and it says a lot about people's gender bias. The revel of the killer's identity at the end of this film doesn't necessarily speak to the audience's bias (see the who-done-it point above) but it does make you think back and wonder if you missed clues because you'd never considered the killer could be female.
There's no supernatural element. In the later installments of this franchise there's consistent supernatural elements bringing Jason back to life, but in this one it's just a lady who wants the camp to stay empty. You don't have to suspend much disbelief to get on board!
