@mgorny The thing that's weird/tough is that almost all OSS communities end up structured this way -- a large foundation of contributors who do the bulk of the work, and people around the edges who fill in the gaps.
I've never seen an OSS project that did a good job of spreading this out over a large group of people.
I'm not saying it makes it OK, but the best thing those "20 people" can do it look out for their own mental health and set boundries. Otherwise the work just consumes.