Yes, and those people are called hobbyists.

Even if you work for yourself, you decide which market to be in, and the market decides what you must build and when.

Sure. I don't have some belief that all developers are incapable of product management. The very best, IMO, have strength in understanding what and why as well as how. But I do have a belief that in some cases, there is value for everyone in having a team with specialized roles. For all products there is a need for product management. And for some product teams, there should be a specialized product manager leading product management.

Interestingly, the push to smaller start-ups and smaller teams does create more opportunities for developers to wear multiple hats. That's a good thing too.

Then they should work somewhere they can do that. Most likely that's a small company or a startup.