Homebrew (after installation) uses its own, bundled ruby runtime and will finish removing any dependency on system ruby long before Catalina is publicly available.
I know, but this wasn't the case when it started. Besides, I believe the parent's point was that nobody uses ruby or perl for anything anymore, regardless of whether it's preinstalled or not. Which is obviously silly when looking at homebrew's internals.
Let's not go overboard - 2.7 will get security updates and patches until the end of December.
> nearly nobody uses perl or ruby at this day.
Well, except for homebrew of course, the Ruby-based package manager nearly "everybody" uses...