This is an idiotic argument; it presumes that having kids in your 20s is the only way to grow or have fulfillment. So I guess a priest or a monk cannot grow as a person or have a wonderful sense of fulfillment? If this is the only way you can grow or be fulfilled, it brings into question your value as a human being.
The reality is that a very significant chunk of the people who have kids in their 20s today did so as a result of a character flaw, personal stupidity, or random chance. Hardly a ringing endorsement. For most people, it does not make sense to have children in your 20s which is the real reason this is happening -- if it isn't rational, most people won't do it. GenX is under no obligation to meet the vacant ideal of anyone.
For women, early 20s are biologically the best time for having children. Men are a different story, though.
I'll say it if Qam won't. The vast majority of childless 30 something and 40 something individuals I meet are bigger children than my children. And by children I don't mean charmingly playful or youthful. I mean self-centered prima-donnas with little or no maturity.
"For most people, it does not make sense to have children in your 20s which is the real reason this is happening -- if it isn't rational, most people won't do it."
Which is why I tell my daughters to live their lives from their hearts rather than relying on their minds to know what's best for them.
There are things one just cannot know until one has aged, has lived, and has observed one's peers live (no one really pays much attention to older people-- people mostly figure that THEIR generation has all the answers.) So, by my reckoning, if one knows in their heart that they are meant to have children, one should go ahead, while one who either does not know that, or knows the opposite, shouldn't.
I was the first kind, so I had children in my twenties. Now, I'm 46 and both are in college. My husband and I are young and healthy enough to do everything we want to (hike, camp, travel, pursue new interests like art) and we have plenty of money and time to do them. Life is great!
One learns and grows from raising children-- not that it cannot be done in any other way as it obviously can, but it can also be more easily avoided by the childless. Parenting tests us, hones our character, and ultimately separates the wheat from the chaff. Just as I know people who say that the Marine Corps MADE them, I feel the same way about parenting-- it MADE me.