As noted anthropologist Sarah Hrdy has pointed out, for most of human history, children were raised by the tribe, not just a lone mom, who was maybe getting a little help from dad. After all, foragers were providing the bulk of what a tribe would eat, and human babies take a long time to mature and become self-sufficient.

“Years before a mother’s previous children were self-sufficient, she would give birth to another infant, and the care these dependent youngsters required would be far in excess of what a foraging mother by herself could regularly supply. Both before birth and especially afterward, the mother needed help from others.” (p. 31) Without alloparents (kin and others besides the actual parents) to help feed and protect them, few Pleistocene children could have survived into adulthood.

The fact that we now for the most part expect women to do this all by themselves is, as you've pointed out, not sustainable. Our culture needs to shift from one where in the relatively recent human past men went out to work and women stayed home and took care of everything for them on the homefront to one that reflects the realities of the times.