Certainly we are all an alchemical output of our nurturing environments and our intrinsic characteristics, and I don't dispute that we could likely dramatically lower the incidence of severe mental illness by improving our culture's capacity for care and solidarity. It's tough out there, for children and adults.

There is no modern isolated Nuclear family. There's mostly broken homes now, and that is the root cause of most of the problems.

Truly, the cause of all this suffering is not enough antinatalism. You've cracked the code.

Actually what they're saying is that most people did not have a lot of nurturing adults in their lives growing up, from which they've learned that the adult thing to do is to isolate themselves and avoid nurturing other people. Which they're presenting as a bad thing. The reason they bring up the "nuclear family" is an appeal to prehistory, in which we probably would have been raised by a much larger social group than mom and dad, to include other relatives and friends, and that this would give us more opportunities to be included and nurtured by a wide variety of people.

You don't need to go back to prehistory, you can just go back a few hundred years before the urbanization brought forth by the industrial revolution. We had millennia of written record by then.