There's no "white" nationality. There's no "objective and measurable fact" that everyone in Thedas is white. It's just like Heimdall being black or the Human Torch being black. There's no divine rule demanding that these characters have some particular skin colour. There's no reason for these characters to have some particular skin colour.
There is a reason for people not to have guns - the technological development of Thedas. It may have been completely arbitrary to start that the setting is medieval, but departures from a medieval setting do require justification or it changes the setting.
Since skin-colour based racism doesn't exit in Thedas, full stop, creating a diverse cast doesn't somehow "break" the lore. Skin colour was never an issue. It was never part of the game. No one ever commented on it. There was never a main or side quest on it.
Culture is not the same as skin colour.
I didn't bring up either of them, now did I? Nobody said as well that thedas was required to have lots of white people only, no one but you, to try and make it seem like that was what was being said. This issue is exactly like the gun issue, people want something that wasn't previously in the game added in future or possibly present installments.
All fine and well, in fact I'd welcome such additions and exapnsions in the game. Having a new nationality means getting a new culture, or expanding on a previously unseen culture, such as the fex or kal sharock dwarves or a clan of dalish elves or even some people to the far west of tevinter showig up. Establishing a nation of origins for these people to explain their different appearances is excellent, because it offers more oppurtunities to explore stories, and allows for deeper characters to emerge with new view points to contribute.
But then they go on to say, "Well we can just make the orlesians asian and that'll be fine", or worse, "we can make every nation have asain "looking" people in the game and that's how it should be done. That's not alright, thats more racist in fact then not having them at all. Because you reduced these people to just being quotas. "Oh, we need 4.24% more asian looking french guys at that shop corner, that'll show we have diversity interest and that asians are part of the games lore."
It's lazy. It's insulting. It doesn't give a nationality of people the respect they deserve. It doesn't improve the lore. It doesn't even raise any meaningful questions because it was obviously made for quota. And worst of all, it reduces these people to being just skin tone and eye shape. It says to asians "You don't have an identity, you have a look. And that's the only thing we care about you for."