It's of no coincidence that your anecdote, anecdotally is completely outside of software development field. While I agree that 20 year old kid highly unlikely

It's of no coincidence that your anecdote, anecdotally is completely outside of software development field. While I agree that 20 year old kid highly unlikely to be a good replacement for an experienced 55yo machinist or a 55yo electrical engineer. The same is absolutely not true in software. John Carmack shipped Doom when he was 23, and had shipped multiple games by then (Wolfenstein, Keen, etc). Many pivotal software projects are made and created by young guys (Ken Silverman, etc), and not set in their ways 60yo Fortran devs or enterprise java devs with baggage and old habits who will use any excuse not to write any code, learn anything new or better themselves - because they simply don't have that energy and drive anymore. Now this quality is useful ... sometimes, but more often than not it is not if you're doing anything new. I'd have a Carmack at any age, but given the option I'd always rather have him at 20 than 55. Back in those days it was rare and unusual if a person started programming when they were 7, 10, or 13. Nowadays it is extremely common that kids start programming when they are 6 or 7. By the age of 20-30, most competent software developers have been programming for solid 7-17 or more years.