The side-hustle culture is a cancer.
> delivering additional value for his employer for which he must insist on additional compensation
Good luck with that.
/r/antiwork is a societal response to this exact sentiment. "Oh make a decent amount more than the national average and still cant afford to retire? Simple, monetize what little free time you have left!"
No, the requirement for a side-hustle is due to the decades of upper management and C-levels taking advantage of employees and leading the stagnation of wages.
The solution to a systemic issue is a systemic solution. The personal responsibility solutions are just a distraction.
Good on the op for getting back some of his time.