During the .com I was quite young, my friends were all doing nascent e-commerce in SF, I was doing Telecom stuff in the Valley.
My friends were all 'architects', while I was maybe one of only a couple of people out of 100 Engs. who were under 30!
I could walk to any cubicle and 'learn for days' from whoever was there about so many subjects. Such specialization that nobody knew precisely what their cubicle neighbours were doing!
You want to know what 'full stack' really means? We did proprietary ASICS, hardware, firmware, control plane software, networking control UI and servers! From the silicon all the way up!
The team was mostly 35-45 and they were amazing, I'll never work with people like that again.
I've run into a fair number of 'young geniuses' and astonishingly talented young folk ... but not the kind I would trust a major project to.
That said, they were a little bit more 'set in their ways'. It was a time when people 'went deep' as opposed to 'wide' generally. Very high degrees of specialization, typically only one professional grade language.