I think that, if in your personal variant of English the words “good,” “bad,” “evil,” and “righteous,” have little to do with “morality,” and if for you “good” (in its conventional moral sense, as in “a good person,” not in its other main conventional sense, as in “a good mechanic”) cannot be used as the opposite of “evil” — then you’re using these words in very specific and peculiar senses that are different from the way in which I use them.
And while it’s absolutely true that D&D has its roots in skirmish wargaming, it’s also true that D&D’s crucial innovations were the ones that started to transform skirmish wargaming into something else - a game in which people played characters who were not actually engaged in warfare as such.
(Also, I don’t actually agree that the only thing that everyone does in war is “murder” other people — although that’s certainly what they do in a certain kind of D&D.)