IMHO, its less about where the work is done (and yes i'm aware that gjs tends to be used mostly as glue, and the same with KDE) and more the fact that I don't want a big heavyweight garbage collected language deciding to garbage collect and glitch some part of the system, or JIT pass recompiling a bunch of code when I first click it. I despise latency in human computer interactions and everyone whines about how its worse on pretty much every common PC/etc vs older devices, yet they go an install hooks written in JITed/garbage collected languages all over the system.

Having those hooks written in compiled languages/etc is bad enough, I found myself regularly cleaning the runas & windows explorer context menus of loads of cruft because the click latency was noticeable, and now not only can one plug in a ton of stuff but it needs to thunk though to JS to do it (and not picking particularly on JS, because it would be just as bad in java or python or whatever other scripting language one chooses).

Its just a waste of cycles, and for projects I work on, engineering time is "cheap". That applies to most system programming if one spends 1/2 a second considering that the code forms the foundation for hundreds of millions of devices all burning energy and the time of their users.