Naturally, that system broke down (via capitalists grabbing the expensive fusion power plants for their own purposes)

This is kind of what I have to give to Niven. The guy is a libertarian, but he would follow his story all the way into such results. And his series where organs are being harvested for minor crimes? It completely flew over my head that he was trying to criticize taxes, and not, say, republican tough-on-crime, mass incarceration, and for profit prisons. Because he followed the logic of the story and it aligned naturally with its real life counterpart, the for profit prison system, even if he wanted to make some sort of completely insane anti tax argument where taxing rich people is like harvesting organs or something.

On the other hand, much better regarded Heinlein, also a libertarian, would write up a moon base that exports organic carbon and where you have to pay for oxygen to convert to CO2. Just because he wanted to make a story inside of which "having to pay for air to breathe" works fine.