So, the proggies have failed in (re) educating people to embrace their world view. It's a bit ironic, since the left professes to favor cultural aspects. They literally bet the farm on the theory that they could change the world, and failed miserably.
IQ was, is and always be the primary human determinant. But, that's not to say science cannot rectify the imbalances. Genetic therapies directed at growing/developing/shaping improved brain mass, neurological connections, chemical miasma, etc - all the critical components of higher intelligence - are just years/decades away.
Add in cosmetic gene applications (hair, eye, skin color, etc), and who will be whom when anyone can be anybody?
If slavery was the basis of successful capitalism; why did the South lose the war? It was the industrial power of the North. Capitalism is based on Industry not agriculture; ask Karl Marx
The Industrial revolution was not based on slavery; therefore Capitalism was not based on slavery.