It's absurd to compare MUMPS with Java. Java is very much used by modern companies on the backend and for desktop applications.

You can still make your SV rockstar programmer salary writing code in Java. Don't they still use it at Google?

Java is still the language of choice for many new projects at Google. Your options for new large server-side projects are, realistically, C++, Go, and Java, arranged in order of how high-level the language is. Java is a perfectly rational choice even today given those options.

Yes, they use it at Google and basically everywhere else. The JS circle jerk is extreme here. JS has its uses - mostly because it is the default language of the web and the web has many uses. That is all.