Depends on the project and team

There are plenty of situation in which all that matters is that the people actually building are happy with it and a tool that literally nobody else uses would be fine.

Indeed, for many engineering jobs (software and other) in some industries, it's entirely necessary to create new tools and use extremely specialiased. Good people will learn how to use (and build/improve them).

I'd possibly go as far as arguing that a sign of a good team is willingness to aggressively use the right tool for the job even if it is obscure or something they have to build themselves.

Sure, if you're hoping to get traction with an open source JavaScript library… git and github maybe be pre-requisites, but for projects of a certain sort "reach" and "adoption" by other developers are the most important metric. (Though, SQLite has done just fine with Fossil, so there's probably a degree of overstatement in the idea that it anything has to use git / be on Github.)