I'm in my mid-30s and definitely can relate to much of what this article talks about. For me this "crisis" started in my mid 20s, although I really can't relate to it as a "crisis" but more of an "awareness".

Around the age of 25/26 I was working as a software developer in SF and having the time of my life. Parties, dating, living in the city, spending all my money on rent.

Then I started slowly but surely to become aware of my age, and the fact that I needed to find a partner. I worried that if I didn't start to think about finding a partner, I might not find one in time and could end up old and alone. So I made a series of rather large decisions to be more (productively) social, and look for a partner. I did that, and got married. Bought a house. Leaned into my career.

Nearly a decade later now in my mid 30s I'm doing pretty good financially and am in a happy marriage of 8 years. But I am left with a feeling of "what else?"

For reasons that are my own, I choose not to have kids. Maybe that's the end of the story there, maybe you can attribute all of this feeling of "what else" to the fact that I'm not procreating and don't have children to pour my extra focus/worry/attention into.

I think that's a weak excuse though, and the real answer is more difficult to understand. I look back on my childhood as a magical, interesting time and modern adult life by comparison is rather dull. Sure you can do things to spice it up, but mostly its the same thing day in and day out. I'm trying my best to make peace with this and enjoy the routine, and have had some success, but definitely can't shake this depressed feeling of "is this it?"

Climbing the career latter is fun, traveling is fun, etc. etc. but none of it compares to that magic of childhood and the excitement for things.