What exactly are you imagining is happening? People just want to use the languages they're familiar with. It does not harm you in any way. You're not going to be forced to start using JS in Bash.
"Why do we insist on using the same one language everywhere?" Who is this "we" you're talking about? Where is this "insistence"? It's not like there is some cabal out there that is organizing a campaign to rewrite everything in JS and also delete everything else.
What does it matter to you that people started a new project, that re-implements functionality of a dear, favorite project of yours, without taking resources away from that dear, favorite project? These people, who are only wasting their own time, who would have never worked on your dear, beloved project anyway? If you don't want to use JS, just don't. Stop reading posts about JS.
"Why do we insist on using the same one language everywhere?" Who is this "we" you're talking about? Where is this "insistence"? It's not like there is some cabal out there that is organizing a campaign to rewrite everything in JS and also delete everything else. What does it matter to you that people started a new project, that re-implements functionality of a dear, favorite project of yours, without taking resources away from that dear, favorite project? These people, who are only wasting their own time, who would have never worked on your dear, beloved project anyway? If you don't want to use JS, just don't. Stop reading posts about JS.