Great question! I never shared this story. I can only answer this from my own perspective and NOT on behalf of the entire project or other devs if you can imagine. And you're correct every open-source project can have this similar situation.
I try to make Mbin as decentralized as possible in terms of development, contributors and no single-maintainer. I hopefully advise that by putting time and effort in writing out the C4 specification: https://github.com/MbinOrg/mbin/blob/main/C4.md. This means that every contributor can become a maintainer. So even today, I'm not the only maintainer and hopefully I will never be the only maintainer. And this goes as far as full access on the git repo(s) as well as Matrix chats.
Recently, a very dedicated contributor did left Mbin sadly without any announcement. This person is still being missed to this day (I hope he is doing well in RL). So bad things do happen, at the same time I hope we as a project will also attract new developers and contributors (even documentation, translation or picking up a simple UI change can already help a lot and often that is the best way to getting started).
I believe it's important to also take some time off. Like in the recent holiday period I forced myself to take some time off. Even then, I also do feel the pressure sometimes. At the same time; nobody is actually pressuring me. Crazy right?. Nobody is paying me to contribute to Mbin. And nobody expect me to spend time on it daily. So it's important to be aware of this situation and know it's mainly in your own head, sometimes just let it go... But you're right, you do feel a kind of obligation.
I also asked among the contributors if you should accept any form of money or NLnet funding or anything in that regard. Our common conclusion was: NO. Because we are doing it for fun, asking money will only create a situation were you might even feel more obligated.
Luckily the state of Mbin is also getting better and better over time. I'm really glad about that. In the past year we really focused on stability and scalability. Mbin also inherited a lot of issues from /kbin to be honest, and we really did some major overhauls to get the stability we and the server admins want and need (thank you all for this!). I can say that we are now in a good spot at the moment, Hopefully we also stay focused on the quality of the code, so the project will still be alive for years to come. Since nothing is worse then inheriting technical dept on top of a huge pile of issues, that is no fun.
Developing software for the fediverse is in general quite demanding work, no doubt about that. On top of the social media drama that often also happens. So the most important part of each open-source project is the community, the people, the interactions we have. The jokes we sometimes make. I can't thank the community enough and in the end we are all part of the fediverse community, so only we can make it fun and lead by example.