Every time people lament changes to the lore that amount to "not every member of species X is irredeemably evil" and claim the game is removing villains from it, I think how villains of so-caleld evil species fall into two cathegories: a) bland and boring and b)have something else, unrelated to their species going on for them, that makes them interesting.
I'd argue Devils, by their nature of being lawful as well as evil, are often interesting villains because of their "species", but it's kinda different when it's a creature literally made from the primordial essence of Evil rather than just a bad dude.
Not all are made from one guy though. Some are just pulped evil in a can. Even with different outlooks on life there are still things that everyone would hate. Like "very specific crimes" to an infant. I say that's enough for pure evil