People weren't in a position to opt out of many things at all, women or men. As a demand that's not in line with what the realities of life were.
The only social safety net in society was families and communities. There were in fact, in Europe at one time, large numbers of unmarried people who for one reason or another opted out of marriage and parenthood - a far far larger portion than do so today - living in mainly same sex communities. Living alone wasn't particularly practical for many, given the degree to which people had to be self-sufficient.
But do you really think the majority of adults would opt out, entirely, of relationships with the opposite sex? Most people don't do that now even when it's possible to have sex without children or commitment.
The modern view of sex is just very alien to many people in the pre-modern world - there is a reason the attempt to have a sexual revolution in the early modern period wasn't all that sucessful all it ended with was bad situations for women, and babies riddles with syphilis and other congenital STIs. It could not be divorced from pregnancy and it could not easily be divorced from disease in the time before antibiotics. A sexual ethic that said that sex should be containied within a monogomous commited and relationship where the father was responsible for his offspring, and the extended family if he dies, was overall a good thing for women and for children.
Women's communes where women just have babies with passing men and care for them communally aren't a feature of many societies largely because most people, including most women, prefer to have relationships with the opposite sex and with their own children. And also because losing the labour of fathers in these equations is not a small thing. Societies of men and women working together often failed because they couldn't do enough, dividing them is not going to make that better.
It's utopian stuff written in novels about prehistoric people based on someone's imagination, nothing we actually know about prehistoric people.
Exploitation by men because they have certain power advantages is something I think JP certainly would acknowledge existed and does exist now. We all know that some social structures can be exploitative, or can cease to be helpful when they were useful in the past. That's different than this abstraction "patriarchy" which pretty much gets invoked, outside of anthropology, to describe whatever someone wants it to describe. It's a bit like gender as a concept, it functions as a ready-made conclusion.