Well, if most JS devs don’t know what the f*ck they’re doing, “developer availability” doesn’t mean too much. I’d rather have 20 fairly good devs in Java, 10 in Python, and 10 in C++, than 5 good JS devs and 35 crappy ones.
In practice, good programmers can pick up additional languages fairly readily. That’s how I built my entire IT career.
The kind of JS devs I’m seeing (who don’t know what the f*ck they’re doing) I wouldn’t trust to program in other languages because they’ve picked up a lot of bad habits. In other words, they’re not well-trained programmers.