kind of a "yes, and", but:

> such a degree of sacrifice wasn’t always associated with raising children

To a certain extent I agree with you that lower standards in parenting made the whole project more doable.

However, when my great-great-grandmother's brother's wife died, my great-great-grandmother had to quit school (about 14 or 15 years old?) in order to stay home to help take care of his baby. Shaped the whole rest of her life.

Responsibilities being split often meant others had to sacrifice in addition to parents, and those expectations of sacrifice often fell hard on women (whether young unmarried or past their own reproductive years).