True.
But under the same logic there could be more brown looking people, no?.
But the setting does give us an answer, because apparently everyone who looks white in Thedas comes from any number of the established countries, but all brown characters come from Rivain, the one brown place amongst so many Europe analogues.
So, unfortunately, race amongst humans does exist in Thedas. Don't ask me why.
To be clear, I'm not defending the devs' decision to create races in Thedas, just pointing out that in a completely fictional setting, it is ultimately up to them how the characters look. For whatever reason we ended up with white people in Orlais and Ferelden and most of the other nations, and you're totally right that it didn't need to be this way.
What is a positive sign is that I think to some extent they are trying to change this. Dorian was white in his initial concept art, and now he's brown. It seems that Tevinter's eastern regions are (as of Inquisition) home to people who look like Dorian instead of, say, Danarius, and I have a vague memory that this is going to come up somewhere in Dorian's conversations.
It is possible to "clarify" the lore to make non-white characters more common than they were in DAO and DA2, and I think Inquisition is probably going to do this. It's not a totally elegant way to make up for what people were concerned about in the last two games, but it seems like a good step moving forward.
(What it might mean, for example, is that if we ever went to Tevinter in the future a great majority of its people might not be white, depending on the region.)