I am not sure what to do about the burnout problem. The way he described it is very on point though. Since everyone working on the project is overloaded there is a great feeling of things only get done if you do them.
Most of my open source work was in the pre-GitHub days when we used mailing lists, not pull requests, to build community. I do think there was something better about that for the project itself as it encouraged a lot more discussion and community building. PR's and Issues become silos and are not great for general discussion. I think they also encourage drive-by contributions which honestly are intoxicating initially but once you see people are not coming back become defeating.
Ironically, the solution from my perspective is the opposite of most advice. It’s not for everyone to become drudging zombies apathetic about their work and just kicking the can, it’s that more people take pride, ownership, and accountability in all aspects of their lives.
Having gone through burnout and a lot of therapy, my conclusion was that my burnout (and I think others too) was caused by being a caring decent person in an uncaring world. There are far too many people who surround all of us who are apathetic and/or incompetent, yet are entrenched, and being “forced” to carry their burden has an amplified effect on the misery we feel when doing that work. When you work with a team that only has accountable, competent, engaged people it becomes energizing rather than draining.
Realistically even if I am entirely correct above, this isn’t a solution. This is just a confirmation that in my experience the old adage “hell is other people” is true and the primary driver of burnout.