That's a simplistic view. That might be true in dynamic urban environments where people compete for intangible resources and success is predicated upon individual merit. That's not so much the case when people fight over collective ownership of land, waterways or mines.
You could say the same thing about the whites/blacks in the USA. But even there they've figured out how to make diversity into the "secret sauce" behind prosperity.
Diversity and immigration of talent keeps USA prosperous today. However, the path to prosperity was built on the backs of captured slaves followed by two world wars which left the rest of the world damaged but USA emerged out with a massive industrial infrastructure.
The earth isn't just a bigger New York.