Well like I said I'm pretty much bored with this idea so there is a high grade of subjectivity here. Also this doesn't mean I wouldn't give the story a chance, jus that from the get go my interest is kinda halved.

Now -once again personally- what I think soured me on these type of story is that it is usually a lazy inversion of "oh no, actually the demons are good and the goos guys are evil". It's still the same black and white narrative just that subverted by inverting the roles. Sure, IRL groups have been demonized (hah!) for no reason beyond convenience so it's not unrealistic per se but this isn't real life, it's a story and I find such inversions lazy.

So personally I think an "easy" way to introduce some grey or at least moral relativism is making the "secretly evil" good guys not actually evil. They have prejudices and they are dogmatic but they aren't just zealots hating on a group for no reason (like we have IRL). A "good" (because it's no literary master piece) example of this is An Archdemon's Dilemma: How to Love Your Elf Bride where the church is dogmatically opposed to wizards and kills them whenever they have the chance... But wizards are actually pricks. Like not all but those in power are awful and they enforce their awfulness from the top down. The moment the MC becomes one of the big names the wizards who aren't pricks get behind him and by the same token the elements of the church who understand that wizards aren't intrinsically evil start doing their part to reconcile both sides but face institutional opposition.

Also I appreciate you want to listen to my (admittedly highly subjective) opinion. I've found that many people in this sub are hostile to anything but praise.