You ask what happens when children can't count on a mother and father being at home for them? Well I might also ask what happens when abuse perpetuates because societal pressures make marriage difficult to escape?
So if marriage is impermanent and a private, exclusive agreement between two parties, then they are indeed isolated. Indeed, abuse and infidelity are among the things which can ruin a marriage, whether or not escape is possible. A bad marriage ruins lives. And so does divorce prevent or undo the damage? How often do children benefit from parents' divorces? If a child gains step-parents then that may increase the love, attention, and wealth they receive. If divorce is a solution to abuse, then should the abuser stop trying, or go back "on the market"? Divorce can free abusers from their responsibilities just as it frees the victims, I suppose.
If spouses divorce, what are the ramifications for aging in-laws? Do mature children still have a responsibility to support their parents? Or is this also handed over to commercial and state interests? Put all our elders into a facility, hire a caregiver, that's what insurance is for? A man divorces two wives and he's on a third; who can rely on his support now? Is he capable to stretch his resources among three families or do all his responsibilities cease with divorce? He's certainly gonna get stuck for child support and alimony to the fullest extent of the law, and his custody is sure gonna be imperiled because the courts rule in favor of mothers, and the law supports them so much better.
Are community supports a drop-in replacement for families? Is it the same when Grandpa hops in a commercial van to visit the senior center instead of being dropped off by his son and daughter-in-law? Does a Meals on Wheels participant have the same quality of life as someone whose relative prepares meals for the whole family?
Sure, everyone can survive without their families or friends. You can pretty much hire people to perform any type of service a caregiver could do. The state can fund all those programs and entirely obviate the need for children.
Is that a Utopian vision for the future, then?
Or creating robots that sufficiently replace human labor.