I don't think it's a problem at all for places to be culturally or ethnically homogenous. I would say the primary advantage of integration and diversity is that

I don't think it's a problem at all for places to be culturally or ethnically homogenous. I would say the primary advantage of integration and diversity is that no culture is perfect in every way, and cross pollination allows for the best parts of each culture to be recognized and used. That being said, cultural exchange relies on a decently high degree of overlap between cultures to establish kinship and trust. There are definitely cultures which are so different that they cannot exist well in close proximity, and so it's inefficient to try to force them to.