Meh, you can say it's an excuse but I think the dialogue and tilted performances are on purpose on a meta level. That part of the film (the characters and their dialogue) is one of the things 'stuck' in the 'nature' of a slasher film. They are playing out their roles with bad dialogue and less than earnest performances because that's their natural state.
The reason I fully believe that is because each and every character does exactly what they're supposed to, the stoner goes out by himself and gets killed, the promiscuous lovers flirt and get killed, the heroic ranger has one last stand against Johnny and gets killed, etc. The one and only time a character breaks their nature is the ending. Kris is SUPPOSED to lure Johnny to the fire tower for one big, climactic battle but she finally breaks her own nature, does the intelligent thing, drops the locket and just runs for her life. I think that's why Johnny continues bludgeoning Colt: the action that was supposed to draw him away never happens. There's a distinct sound cue when Kris is walking on the road that I think is the indication that she's fully out of the nature of the slasher film, where she finds herself in the real world, talking to the woman and having to deal with the real consequences of his traumatic experience and the depression and anxiety that comes with it.
I would say you're missing the forest for the trees if your main complaint is the characters, dialogue and performances.