I think the difference is, boys and men were having fun but also working on their career and they have responsibilities.
Today boys don’t grow up. They don’t have responsibility, they don’t think about their career. Many of them are still acting like kids into their 30s. While women are advancing their career and maybe they see anti man propaganda and there is this whole women empowerment going on. Then when we go to couple up... women don’t want to couple up with these men who are still children, so they decide to wait to get married much later or not at all.
So we have this feminism “issue” and we have this Peter pan problem and it’s causing problems.
I have observed just as many boys as girls checking out from a career or marriage. Sometimes both, sometimes one or the other. The excuse for checking out of marriage is that it's an outdated relationship style, too much work, and just leads to divorce. The excuse for checking out of a career is that CEOs and investors don't care about people, they just care about extracting profits - meaning that you are a disposable commodity, therefore everyone will eventually get pushed into the gig economy meatgrinder anyway. The excuse for not buying homes is that the boomers have over-inflated the real estate market so that they can retire on everyone else's dime, because boomers only care about themselves. Etc.
It has not been uncommon since women's lib that some women have prioritized their career over marriage and children, until their late 30s and 40s - and then they suddenly decide they want these things, but the only single guys around are either divorced with kids and baggage of their own, or guys that have done the same as they have and don't really have the time or willingness to prioritize a relationship, or guys that checked out of commitments and are coasting. And then it's "there's no good men anymore," when there very much is, but because they're good they're already unavailable to you and aren't coming running just because you snapped your fingers and decided you wanted something. Just like it is for men that do the exact same thing.
You can say it's a boy problem, but I've sat with some of these guys, and seen them send out texts or snaps or instas or whatever, and the girls come running for a night of fun and then they go away, too. Culture is changing. I don't blame millennial when they got handed a society that doesn't work for them. But many of them do work very hard, even if it is very differently. And they do care very much for each other, even if they do that differently, too.