The pattern is familiar: * open source project * success * no monetary reward, maybe just cost * burnout * project abandoned This is why I don't try to make any open source projects - what's the gain? I'd only do it if it paid money. If people aren't willing to pay then I'm not willing to work.
This is an Anti-Pattern in OSS. Start a project to build something you want/need. Update it as you want/need more things, but don't build other people's businesses for them.
Yep. Scratch your itch. If someone else wants different features then let them add them or compensate you for your effort, unless of course working on those changes is interesting for you or would help scratch your itches. If you do it for the "interesting/fun" reason make damn sure the requester knows that if that interest/fun stops then free work on the feature will stop and it might get removed completely if not maintaining it becomes a security problem or other burden.
"But what about the community?!" you hear them cry. Fuck 'em. Or at least suggest they do something for the community they care so much about by putting in a bit of effort in to maintain it, maybe forking your project to do so while you deprecate the feature and work on things that are interesting or useful to you, or paying you to work on the bits they particularly want and you don't. Your mental health should be much higher up your priority list than doing work to help people who (call me cynical, but...) probably wouldn't do the same in reverse.