Haven't read the full thread. I'm mid 50s. Lots of exes. Never married.
Have never bought a house with a man. Have moved into their place (one ex), who ended up calling the shots over our day to day lives as it was "his house".
Then had two more long-term exes after that (not at the same time
).
First was an Alpha male type who spent most of his time at my place - I wouldn't go to his as it was a tip. He just ended up taking over my space. Football on TV constantly and trying to tell me what to do. Poor love. He had no idea who he was dealing with. 
Second guy was a gentler, quieter type. But gently, subtly, he took over too.
So, it is my experience that men are either overtly or subtly domineering and, often, pretty selfish. They are brought up thinking men are more important than women and deserve to get their needs met first and that we should just accept it.
I have no plans to ever live with a man again
). Two divorced pals of a similar age feel the same. Though my sisters (early 50s) are happily married, one in a long marriage with teenage kids, and the other has just begun Marriage No3, so the rot hasn't set in yet, lol.
So, on balance, I think it's an age thing. Older women have been there, done that. Younger women want kids and, often, marriage. And as women we are socialised from a young age and expected by society to find a man, get married and have children. Fairytales of princesses being rescued by princes, being given dolls as toys, etc. Some, though not all, women feel a failure if they do not "achieve" marriage and children.
So when women say, or think, they are unhappy without a man, I think it's because of their belief system, and society's, that they are a failure if they haven't got a man.
The happiest two women I know are in a sexual relationship with each other.