Most people I've encountered have had a legitimate reason to dislike the game.
Take I Hate Everything, for example.
I also have a reason for disliking it, and my reason is that it gets boring and repetitive after, like, two nights, and also that it uses jumpscares instead of some other way to scare the player, which feels kinda... lazy. FNAF also feels like more of a strategy game than a horror game to me.
EDIT: I also just realized how all over the place I am right now in terms of what I think about FNAF. Maybe because I swapped to a new AD(H)D medicine prescription thingy, because it's been like this for what I think about other things today, too. :^/