Hey,
I'm still using django-mptt in a few projects which still are in active development (some over 10 years old these days); also,
https://github.com/feincms/feincms still uses mptt under the hood.
I've switched all new projects to use
https://github.com/matthiask/django-tree-queries/ (feincms3 depends on it) and I'm very happy with it. The performance of recursive CTEs is very good, sufficient by far, and there's no way to corrupt mptt attributes (since there aren't any). Also, there's no freeloaders complaining about missing release notes etc. etc. (As a user of packages I understand them, but my solution was always either to abandon ship or help out, not complaining.)
So, long story short: I still have commit and PyPI access, I still review pull requests if I feel like it and I may even push a release in time, but the knowledge that people will complain about missing release notes make it so much harder when I'm not scratching my own itch (which luckily is getting smaller and smaller)
I hope this clears things up. And maybe someone even steps up to help with or take over maintenance duties.
Best regards,
Matthias