Ruby is changing. I doubt it will ever be as big as the Python world, but I can see it coming back into fashion. I’ve been paying attention to the community and it’s still very active.
I think there's a lot of burnout in the JS ecosystem, and many are looking for the efficiency of Rails. However, I'm not certain if Ruby on its own is gaining more of a foothold. For a few years it looked like you'd seen more Ruby generalists with tools like Chef and Puppet, but I think Docker has taken a lot of wind out of those sails.
And then Rails 6 came along and brought NodeJS by way of Yarn and WebPacks. I'm still pretty light on deep Rails knowledge (currently doing my first non-toy project with it), but I was not pleased to see that this pile of bloat now appears to be a requirement.
If you're interested in front-end performance, having a webpack build pipeline for your frontend assets is quite useful, especially if you want to leverage libraries like react or vue and build interactive reusable components, or leverage existing ones.
Tree shaking, minification, chunking, splitting, etc. will help you deliver a faster initial page load, which is a better overall experience and is also factor in search ranking for your public pages.
Front-end engineering has changed because users expect interactive experiences. Rails has an opinionated way to solve this differently using turbolinks and Rails UJS. A very significant proportion of folks don't want to go that route, enough for it to become the default.