The “theory” is far too simplistic and utterly fails to take into account anything other than a single variable.
It really doesn’t; it merely assumes that there us one factor, which if not dealt with, will continue to cause an insurmountable disparity.
And watch who you call simpleminded. Some of the greatest talmidei chachomim of the generation, a couple of whom I spoke to personally about it, agree with the theory.