One of those key ideas was openness to other cultures and civilizations. The West didn't take the NIH (not invented here) attitude some places took and thrived. But the Renaissance eats it own children - as intolerance creeps back into the Western mind.
Most of the intermingling of peoples in Europe during that time was with other western civilizations. You are mixing apples and oranges on the false assumption that all cultures are created equal. We see none of this in the animal kingdom. Why would it not be the same for humans?