That would make sense in a world where there is no good like BG3 or WH40K or Diablo, where the supposed paragons are as demonic as the demons and the bad guys are as likely or more likely to be heroic as anything that looks noble or beautiful, but if you allow for the existence of actual good (rather than just "hats") instead of having a grim dark setting that suggests any pretense of good is almost certainly hypocrisy, then I think you have to have something more subtle going on. You have to create a world where not all evil is just victims who are looking for a way out. Not all good is hypocrisy. Not everyone who is oppressed becomes an oppressor. Not everyone who is successful or advantaged is a victimizer. Not everyone's reasons for joining a cult have to be sympathetic or rational. If the terms have any meaning at all, then they have to describe something different from each other, otherwise why bother using them? If a demon or an angel is just a mortal with different forehead bumps, why apply the terms to them?
I mean, a lot of tables I think do make that decision, that the labels aren't meaningful so they won't be used. But I find that a bit of a copout. Even if you don't believe in the ontology of good and evil in the real world, in the fantasy world it's an assumed thing most of the time, so I feel like you ought to engage with that.
And, of course, I do think that there are people who will insist that despite the appearances to the contrary and all the corruption, there is something importantly different in the WH40K universe between the philosophies of Nurgle and the philosophies of the Sons of Vulkan, and that while maybe no one's virtue (especially when taken collectively) is pure that there is virtue. And that is itself interesting as an exploration. Is there still something pure - a diamond in the muck - in a situation as corrupt as WH40K? Can you still find a place to stand where you can legitimately condemn the followers of Nurgle as objectively wrong?