* Certain kinds of generalists with skills at starting and running successful companies start and run successful companies

The generalists that don’t have the particular intersection of skills to be CEO end up being outcompeted by specialists for specialized roles. See: poor wages and working conditions for unskilled workers, who certainly have skills outside of work, but no skills that matter enough in the economy to get specialized jobs

Same is true for specialists. Only certain kinds of specialists will be paid highly.

Picking something that is not only interesting to you but also needed by the market is generally a good idea if you want to earn money. Otherwise it’s just a hobby.

"Picking something that is not only interesting to you but also needed by the market" is not always a feasible option. Good for you if you found an in-demand job that is interesting to you, but not everyone can find that.