Not pick on Ruby, but is it a good reason? You've got 1 million lines of code and they’re written in Ruby and rewriting it would be, ah, untenable. But would ruby be the best choice today if you were starting from scratch? Maybe! But sheer inertia isn't a good reason in and of itself.
He didn't say inertia, he said mature. It take a while for a language/platform to develop a solid ecosystem and stabilize. That absolutely has value, and is something you can't get out of a new system no matter what novel problems it solves.
As far as new apps go, yeah I think it's still pretty optimal for a huge swath of web apps, especially for early incubation when you have <20 engineers and you need to move quick. Not if you need web sockets, or other concurrency / performance critical applications though.
Yes, I'd also think it's a great idea to build new apps in a language currently undergoing a distribution & supply chain war between the interested parties.
