> You also ignore the flagrant existence of powers that were not diverse. The Phoenicians interacted with a lot of cultures and influenced them very deeply, but Canaanite society was highly insular. Viet Nam was a powerful society that expanded continually, but it engaged in aggressive replacement colonialism of peoples it conquered

These societies hit scaling limits precisely because they failed to diversify.

> Diversity in a real sense requires a collection of disparate, conflicting identities

Not necessarily. One can deprioritize the points of difference, or redelineate on the go. Americans incorporated Italians and Irish into whiteness; Romans Italians and later provincials into their citizenry.