Those McKinsey/HBR studies are trash. They privilege the hypothesis, overlook the obvious ecological fallacy at play and add in a bit of a sampling bias for good measure. The fact that East Asian Economies are all booming and exporting globally with ~0 diversity and unique cultures ought to refute this notion. I'm sure there is some no true scotsman line you can play here about how the true meaning of DEI, and I would agree that the stated goals of DEI are all laudable. But in practice these initiatives often amounted to unprincipled discrimination and venal power grabs, which is why they are so widely despised.