JK Rowling never has to work again in her life because she wrote a couple of books that were exceedingly popular. Because she doesn't have to work, she's not been forced to come up with new stuff. How is that not stifling?

You pick one example and ignore thousands of writers who didn't even return costs after publishing a book. Also, as another example, a great Russian 19th century poet and writer Alexander Pushkin left lot of debt after his death. He supported publishing other writers but it turned out to be a commercial failure. Maybe this fact will make you less unhappy about supposedly unclouded lazy writer's career.

She comes up with new stuff all the time. She's had a separate career as a writer of thrillers, and is still working in the PotterVerse.

She's an awful person for other reasons, but that's beside the point here.

Reality is most trad-pub authors have full-time jobs anyway to pay the bills. If you're not one of a handful of publishing superstars, trad-pub pays incredibly badly as a result of corporate consolidation and monopoly dominance.

To be clear - there are far more people living parasitically off investments, producing nothing at all and extracting value from everyone else, than there are talented creators living the high life.

She made enough money selling books by the 5th book that she'd never need to do anything again and live better than 99% of people on the planet.

What do you want?

She's not allowed to make money selling books?

The same analogy could be applied to business though. Some Colonel invented a fried chicken recipe and started a chain of restaurants, now he doesn't need to work anymore.

In my opinion, if someone creates something that has value for a lot of people, they should get rewarded for it.

...it's worth noting that J.K. Rowling is still coming up with new stuff. I quite like her ongoing Comoran Strike detective series. They're published under a pen name, but it's Rowling.

Notch (Marcus Persson of Minecraft fame) is probably a more compelling example.