Since my early 20s I've always considered the idea of evil as an objectively true concept horrifying. Labeling something as evil is always an excuse to abuse that being. I'm a moral relativist, I think morals are arrived to out of a societal conversation. There is a biological basis for some moral thought, empathy and social cohesion is needed for stable societies and continued evolution, but morals should not be limited to such base reasons. You base morality on lessening suffering and extrapolate from there. With every generation, every technological leap, and every new concept of personhood, you broaden the scope of what being moral is, and what beings are covered by those morals.
It's not like evil as a concept is actually needed for action/adventure stories. If someone attacks you, I think you are justified with responding with lethal force (most of the time. For example, if you have a party of demigod level PCs and get jumped by common thugs you should probably not outright kill them). All an antagonist needs is to be driven by pride, greed, or zealotry to be a threat worthy of attacking.
Monsters can also exist, being uncommon things corrupted by magic to be inherently dangerous and impossible to reason with, but monsters do not create societies. If you have a stable society of a creature, they are not monsters or evil, just alien in thought. Meaning that they can be reasoned with, it's just difficult because they have a fundamentally different way of thinking. At the very extreme end, you have things from another reality that are so completely alien that their existence in the common reality is inherently dangerous. Such beings from untold realms corrupt the local reality in order to exist properly. Such things can't live peacefully together, at best they can just realize that they need to stay separate from each other, but if they thought that they wouldn't be invading the other reality in the first place.