If we´re still talking about D&D I have to point out that unlike the Tel-quessir could claim the primal war between Corellon and Gruumsh for their heritage and the dwarves claimed to have been forged from the rocks of Abeir-Toril itself, humans had no unifying creation myth. In fact is one of the few races that exist having originated since before written records existed and were frequently considered one of the creator races, and humans are found in almost every world in Abeir-Toril, and many other planes of existence like the Demiplanes of Dread in Ravenloft.
It is canon that the humans in Thay or Mulhorand were first brought to Toril through portals to another world created by wizard rulers of the Imaskar Empire so they also exist in other worlds outside Toril. So the "it makes no sense that a Human population that appears to be very sedentary and not very well mixed in universe appears heavily racially mixed" could be applied to other worlds but not in D&D. Humans, unlike most other races, did not emerge as a whole but rather in several places at once, coming from elsewhere, thereby resulting in its diversity.
Sc:
↑ Reynolds, Forbeck, Jacobs, Boyd (March 2003). Races of Faerûn. (Wizards of the Coast), p. 80. ISBN 0-7869-2875-1.
↑ Brian R. James and Ed Greenwood (September, 2007). The Grand History of the Realms. (Wizards of the Coast), pp. 5, 6. ISBN 978-0-7869-4731-7.
↑ Rob Heinsoo, Andy Collins, James Wyatt (June 2008). Player's Handbook 4th edition. (Wizards of the Coast), p. 46. ISBN 0-7869-4867-1.
Changing the topic the main problem I got is that Politics are anywhere when more than 2 humans gather, but it´s frowned upon when it comes to videogames or other media. And when I say politics I mean "politics that people think are relatable to the real world and are against my beliefs"
I mean, there are lots of stories driven by politics as a plot device: The Imperials vs the republic, families killing each other over the power of the throne, a warlord trying to preserve the survival of the species by reducing the excess of population vs the avenging heroes that want everybody to survive, etc atc
But when it comes to themes like fascism, homophobia, transgender, racism or something that strike too close to "modern, real-world problems" that creates a backslash and it´s frown upon like it´s "second class plots" and "political" and "take this away from my preferred series/movie/etc" when sometimes is related to what the story wants to tell us.
Maybe sometimes could be classified as forced or preachy, indeed, but the pertinence of those values to the plot is for the creator of the story to decide, the writer is the one that decides what he wants to tell us with his story and what is important, not the reader.
