I don’t agree with your assessment. The examples you showed are/were top authors. If they no longer post here it’s for different reasons.
Onboarding is not an easy task. I think we are doing just fine. Maybe slow, but still growing.
That’s the beauty of the open network. Everybody can join or leave as they please, as many times they like.
I wouldn’t worry too much about grand scheme of things. Human behavior is not predictable. It is more productive and rewarding to focus on things that matter most at a given time.
Do what you think is the best, if it works great, if it doesn’t who cares. :) End result we did what enjoyed anyway.