I don't think this is true at all. No doubt I've missed a lot of discussions you've been in, though. I'm pretty new to ENworld.
There are some enemies which it makes sense to have as supernatural evil or as able to be killed or destroyed without moral qualms. Demons. Undead. Constructs.
Then there are enemies who wilfully choose to do wrong and threaten others, like those cultists. (Speaking as someone who's studied comparative religion and sociology, yes, in a sociological sense a cult is just a small religion, but a cult which kidnaps and sacrifices people is still evil). Or like bandits. Or marauding raiders.
Then there are predatory alien creatures with whom we can't communicate (Ropers, for example, among many other aberattions). Unnatural creatures of inimical magic who prey on humans and can't be reasoned with.
All of these are good options for antagonists without the same quasi-racist baggage/implications of describing an entire living, speaking & reasoning species as evil. IIRC James Maliszewski in his Dwimmermount campaign went with Orcs (his are pig-faced) being genetically-modified swine/boars anthropomorphized by magic and possessed by demonic spirits.
I think even in a regular D&D campaign world you could still reasonably have Orcs as black hats if your world also includes orcs of different cultures who aren't black hats. If THESE particular orcs are villains for cultural reasons/out of choice, but these OTHER orcs are not, then you avoid the racial essentialist stuff. I don't have to identify the villains by their tusks or green skin. I can identify them by the Eye of Gruumsh painted on their shields.