Those are very bad examples that prove the gp's point. Sure, flexible and multitalented people are a huge asset IF they get their big break, if they get involved in a startup at the right time in the right industry, if they are lucky to not get crushed by abusive players etc. etc.
But the chances of success are very slim, you likely won't be John Carmack. For every Carmack there are thousands of failed game developers who never got their break. Starting a tech company in 2022 is very different from 1992 even if you get to Carmack's skill level. Meanwhile, holding a job is something that always works and being a specialist in a high demand area is strongly correlated with financial returns.
I write this as somewhat of a "renaissance man" interested in everything from engineering to coding, to economics, to political science, to philosophy - and even holding advanced degrees in these topics. Sure, I can make my paycheck in tech, but without a managerial track record and access to the upper echelons of capital and corporate power I won't be recognized as a critical asset for an organization nor will make "Kubernetes expert" money.