The kurkans are representative of the ottoman empire or the middle east. Khan/kan as in Kurukan also means king or lord in Turkish. Historically, Europeans even while admiring the middle east/ottoman empire for its advancement and "exotic" culture (orientalism) still frown upon it and deemed it as barbaric due to various reasons like difference in religion, the ottoman empire not having family ties with the other european aristocrats as well as ethnicity. So it's more an attempt to be historically authentic and portray the relationship of europe and the ottoman empire/middle east than the author being racist
I noticed that the author specifically chose darker skin color for the kurkans which they call them “barbarians” and literally porcelain white for the royal family and the rest of the kingdom are also white. I kinda interpret that as like “white superiority” and how the white ppl are seen as ppl with manners and etiquette meanwhile the kurkans are literally seen as the opposite vulgar idk inferior ppl. I also noticed this in other manhwas