So as previously mentioned, it is NOT better to have two parents than one.
All studies with any credibility at all, show that if the income is equal, there is simply no difference between the outcomes in terms of depression, academic achievements, health, involvement with criminal justice system, between children of lone parents and children of two parents, if you weight the data for income.
In other words, it's not how many parents you have, it's how much money those parents have. The children of lone parents do on average worse than those with two parents, simply because lone parents are poorer. That's all it is. And if the lone parent has a degree, even being poor doesn't affect the results.
You can scoff at the idea of patriarchy as being last century, but given that poverty is still the punishment for being a lone parent, I don't think you can argue that the effects are last century. In parenthood or anywhere else.
All things being equal, it's better for parents to have as many adults supporting their parenting as possible. Patriarchy has arranged society so that women are isolated at home on their own in many cases, doing most of the parenting without the support or help of anyone else. Whether they're married or not.
And it's irrelevant whether women actively choose single parenthood or not, standing by the argument that two parents is some sort of parenting gold standard, does you no credit. It's that sort of attitude that ensures that far too many women do stay in abusive relationships they shouldn't do - because they're aspiring to a gold standard that is actually full of shit for them.