This is the classic theological definition of evil. Evil isn't the anti-good, it's the absence of good. Good is typically regarded as some kind of selflessness or care for other, so evil is basically selfishness. There's nuance, but I wanted to support the challenge to dualistic world view.
A "theological" definition doesn't really work in a world where there are actual gods and some of them actively want to cause suffering. The theology of D&D (and most other fantasy settings) is not the theology of Earth Christianity of the 21st century.
Of course. But at the same time alignment is under the domain of gods and it's part of the cosmological structure itself. I wouldn't think one can simply declare to be outside the purview of morality.
Of course it isn't out of the purview of morality. It is morality. Alignment is just a simplified way of stating the morals and ethics of a character without going into detail. I'm just saying the theology we have in our world is not the theology of D&D. Evil is not necessarily describing the same thing it may in our world.