An argument could be made that the entire capitalist system is built upon uncompensated labor.
This is kind of an odd damning of capitalism, because no matter how we organize society, there is going to continue to be mothering so long as our species is to survive. And whatever societal system we may have, that society is going to be built in large part by mothering.
However, I think on net it is still more economically productive, at least in a large portion of cases.
"Economically productive" in what way? If you want to adopt a short term perspective of a particular nuclear family making X dollars over Y years, maybe.
But that's a rather shallow and irresponsible way of looking at things without accounting for what's better for the future society of our descendants, economically and otherwise.
What in most cases will produce a better quality of individual, a child raised at home by a loving mother, or a child shuffled off to some "childcare" to be looked after by a minimum wage worker absorbed in a smartphone half the time?
(Not that all non-motherly childcare is like that, but you get the point)
This is kind of an odd damning of capitalism, because no matter how we organize society, there is going to continue to be mothering so long as our species is to survive. And whatever societal system we may have, that society is going to be built in large part by mothering.