I think a technology must continue to change and adapt to remain relevant. I see Shopify as the main driver of current improvements to Ruby (the core features of the most recent release, and the upcoming release, were mostly due to Shopify as I understand it). I don't see smaller companies doing these improvements and I think without them Ruby will (slowly, because it's used in some big places) fade away.
They're in a different class to heavy hitters like Shopify and Github, who will gain a lot more from investing in gradual improvements to Ruby's runtime at the scale they operate at.
I'll contrast it with JavaScript, which has tried to assimilate every language pattern under the sun over the past decade and is intensely difficult to maintain a stable stack with, even if it's better now than it used to be.
I hardly hear about new projects being started with Rails as well...
It may be that after years of working on other technologies, you just aren't passing the filters anymore. When we were aggressively hiring Rails devs in 2021, we specifically searched for the seasoned Rails devs that could hop in and get going. I've found less appetite outside of the big shops (Shopify/Github/etc) to pick up junior Rails devs which isn't great.
I don’t think this makes it dead or dying though. It’s stable and entrenched while JS has taken the place of the golden child.
One complaint I’ll grant myself is that library development is a little less prolific this days. Again, there are well-established solutions to a lot of problems in Ruby so you’ll have a go-to collection of gems, but it’s more often the case these days that something doesn’t have much library support and you’ve got to roll your own.
It's used in many companies, new and legacy.
I'd be very surprised if the decrease since then is out of line with the rest of the industry, regardless of tech stack.
The continuing work on the language and its performance is impressive, but Ruby (and Rails) themselves have the honour of being stable, tried-and-tested solutions for rapid application development. Is it as exciting as the latest and greatest serverless lambda framework in Typescript? Not really. Is it a dependable workhorse? Absolutely.
At some point you might be successful enough to justify a rewrite into something else, but a simple Rails app will take you a long way with little effort.