Software in general has a burnout problem. I am regularly stumbling around like a zombie by friday afternoon, and that's just for my actual, paid job. If you added maintenance of a large open-source project like Rust ... I don't see how I would manage it, at least without letting my health -- and probably my family -- suffer for it.
I know that some people are fortunate enough to be paid for their open-source work, but that doesn't mitigate the burnout from software engineering itself. Add to that baseline stress the fact that your customer is "the internet" and feedback is often coming from "whoever is currently angriest," and it seems wildly unsustainable.