First of all, this movie can’t be taken seriously. It’s a dark comedy / horror movie parody. If you don’t like dark comedy, then it’s not for you. If you want to take it seriously, then it’s also not for you. Overall it’s very funny, and sometimes it even makes you feel bad for laughing (hence the dark comedy), but it’s not particularly scary and the plot is basic-I think intentionally so. The basic plot worked perfectly to push forward the comedy of this obviously ridiculous and strangely fun idea of a horror movie. Not for children. Not for someone easily disturbed. Not for someone without a sense of humor.
-side note: the actors must’ve had so much fun in this film, it’s crazy to see a bunch of rabid children running full speed at some screaming adults and playing with disembodied limbs.