I think that's starting from a mistaken premise. Why expect parents to cope? Parenting takes an amount of empathy and patience and care that many people simply do not have and will not have.
In pre-modern society the nuclear family made sense, but at what point do we say, being someone's biological source gives you no particular right to control their life and the task of guarding and raising children should actually be given to those who can do so humanely? Why try to retrain inhumane parents instead of just not subjecting kids to them in the first place?
If you look at the much bigger picture—children who are gay or trans, children who date outside their race, children born into cults or to antivaxxers, children born with disabilities that expect particularly uncommon levels of support from parents, etc. etc.—the problem is simply that we assue that your physiological ability to engage in tbe reproductive act means that you're fit to be a parent. There's zero reason to believe that.