I think people tend to mature as they age
Yup, so let's spell that out in advance. If people change (which they do) then marriage and kids or any kind of commitment is a really bad idea. It's a bit silly to entangle lives if one or both are going to mature and decide they don't want to be with the other one.
Threads like this help educate people in what's coming, and it can be easily avoided.
(well some of them), and the loss of youth does not diminish their value, as you seem to imply.
I didn't remotely imply age diminishes someone's value nor do I think it does. (Not even sure how it would.)
So why would so many women reinforce this idea on this thread? You might not have experienced this yourself or it might be an uncomfortable truth you'd rather not address as you'd have to take some accountability?
Not even sure where you're going with this. There's nothing uncomfortable about it, there's no need to take accountability. Women don't want to spend their lives with men, or at least mature to a point where they don't. That's fine, nobody is saying they should.