I'd broaden the question about sustainability. I haven't worked deeply on OSS, but have worked with a number of other volunteer organizations or efforts, some on my own and some with a community.

In all cases, there needs to be some payback to the folks putting in time. And it can't just be money, because volunteer organizations never have enough money to compensate appropriately. Otherwise they'd be businesses :) .

Other forms of compensation:

   * fun, as you outline
   * recognition from others
   * impact on the world
   * legacy/connecting to the past
   * satisfaction of helping others
   * increased leverage toward other goals
   * learning new skills
   * connection and community

I'm sure there are a dozen others. But recognizing and fostering these benefits is critical to OSS surviving.

Fun is, by far, the biggest reason I can identify why I work on some open source projects and not others these days! I think it was also true in the past, but to a lesser extent. Docker circa 2015 never felt like a job at all and the early Dockercons werre a thing of legendary entertainment!

A couple of things have possibly conspired to make more established projects less fun in the past few years:

- we're getting older; as maintainers age, I find it's just harder to make time to go to hackathons and socialise with the younger generation, much as I would love to. Too much real life stuff on. The pandemic also established a 'before/after' and conferences just haven't been the same level since for me. I'm not sure if I changed or the conferences did.

- obviously LLMs, since they add a layer of interferences between both the demands on my maintainer time (LLM generated PRs) but also how much I need to interact with other people to solve a problem. I made plenty of online friends over the past three decades figuring stuff out together over some obscure library, but group debugging seems less important now if you can chuck it at Fable.