I rather like the idea that the primordial humanoid races are Orcs and Elves as different aspects of the Creators (whatever that means). Because they are so dissimilar, it makes sense that humanity would arise from their union. I am not sure whether that should be a thing still known int he world, though, or a "secret origin" that somehow ties into a bigger campaign story.
But if that is true, what do we do with dwarves, gnomes and halflings? Are they even further "diluted" or "degenerate" descendents of orcs or elves, or are they something entirely different. And if so, how and why? Are gnomes dwarf-halfling hybrids, or just an evolutionary dead end? Where do other humanoid species fit in, liek gblins?
In one campaign world I created, goblins and gnomes were both fey and in fact the same species. But if they veered toward "good" they looked like gnomes, while if they became malign they looked like goblins. This is literally the nicest I have ever bene to gnomes in any campaign I have run, because I allowed them to exist.