I would, kindly suggest it is, A standard, in fantasy, (and indeed a prominent banner), but not the sole banner.
The Song of Roland, in the character of Fierabas, the Saracen Knight, has a conversion of a character from ‘evil’ to ‘good’, by the moral terms of the work’s ethical framework.
The Lord of the Rings, hinges upon the pity and mercy of Bilbo and Frodo.
If Bilbo slew Golem, then Sauron wins!
More importantly, Tolkien did not focus on Orcs. We know from The Silmarillion, that Morgoth, tortured elves that had not seen the Blessed Lands to make Orcs.
One can make an argument that in Tolkien world, there are instances, taints of Evil that can not be removed....except perhaps in the Blessed Lands.
Melkor, could not be reformed, we don’t know about Orcs or the burden of Frodo.
Which is a long winded way of saying, even the banner you are flying, has exceptions.
The Conan stories are largely amoral, (some might argue immoral,)
The tales of Lord Dunsany, amoral.
Norse mythology and Icelandic Sagas, amoral.
Tristan and Iseult, The Well at the World’s End, and many other chivalric tales are largely amoral.
Your foeman, is your foeman in these stories due to opposition of the protagonist’s goals, not due to some cosmic, inherent blemish of evil.
This is also, a prominent banner and trope of fantasy literature.
I never said there were not other tropes. Every group will have to decide what works for them.
I don't have a problem with that. Well, I have a problem with relative morality in a game where orcs are considered CE meaning that it's just their culture but that's a different issue.
If CE is defined only by relative morality then I don't think D&D really works. After all if that's the case than even Asmodeus isn't really evil because there is no such thing as evil.
It's just a game, I don't mind if it's a bit over-simplified here and there.
P.S. I also disagree with relative moralism on an individual level even in the real world. Some people get they're jollies harming others. That fits my definition of evil.