Excuse me? What exactly are you implying here? That CA and mod makers for Total War are racists? Ridiculous assertion.
I think there are just more interesting conflicts that a mass audience in the west would know of and are taught about. That's why they cover fairly well known periods, on top of being based in the UK. I think the wen't with something like Thrones of Brittania for the period being popularized recently by things like The Last Kingdom and Vikings series. The hype. They have had middle eastern and muslim factions (in particular) featured heavily in Medieval 2 and the Crusades. I think something incorporating these Muslim factions into a medieval world again in general would be a much better choice for an era, but even that might be getting very stale at this point. I think something in the 16th century + would be better, for a new take on historical combat, and a change of scenery featuring maybe the new world, Africa, India again. A well redone Empire would be great - especially with how they are dabbling in merging giant campaigns in Mortal Empires.