My personal impression was that Rails has matured and there aren't as many open problems at this point-- there are agreed upon patterns and gems for most things you want to do in creating a web app-- or at least a relevant SO answer that is the first thing that comes up when you google a problem or error message.

I know that isn't exactly what this question was measuring but I'd expect engagement for Ruby in general to fall on SO. Compare that to the current wild wild west of JS frameworks where everyone seems to be doing their own thing.

Well the SO community is definitely the representative of Web Developers community. And since Ruby is mostly Rails, and Rails is a web development stack, this tell a lot.

And I think that is the biggest problem with the Ruby communities in general, NO one cares about Ruby is dying. Not Matz, not DHH.

I noticed the same. Maybe the results are skewed a little bit by the SO audience but I think it's a real trend.