You might have a point there but I'm talking about... uhm. The best example I can come up with right now is Swiper from Dora the Explorer. Sorry. The kind of antagonist who is just there because the writer thought the story needed an antagonist.
Another example would be the goblins in Sunless Citadel. There's nothing in the plothooks that tells the players they are evil, and yet the adventure expects that the players will invade the home they've been living in for at least 13 years and slaughter them all. The only thing they might have done that could be percieved as evil is owning a barrel of elf pudding and there's no way for the players to find out this information except by finding that barrel.
In contrast, skeletons and zombies on Golarion are evil because someone killed them, took their soul and mangled it and then put it back into their rotting corpse. Demons are the reincarnations of the sins of mortals cast into the abyss. Mind flayers eat the brains of what they consider to be lesser beings, much like we might eat the meat of animals. For them it's a necessity to survive, but we would consider that evil. Even Javert in Les Miserables has a reason to do the things he does, even though it's a flimsy one at best.
All af these are better justifications for being evil than just needing an antagonist for the story.
I'm curious if you can come up with an example of a straight-up evil villain who isn't boring or bad. I'd love to hear about those.