You do know very well that all of this is going to happen someday. Everything will be re-written in JS just because it's possible. And numbers will show that those solutions beat C++ in speed and resource usage, like VSCode does.

What does VS Code beat in speed and resource usage? Be fair and compare it to other software with only colourization, Git support and extension support.

JS can get close to C++ in speed but the same program in JS will always need more memory.

I doubt that. C++ programs have always tons and tons of memory leaks.

Which you can fix if you're competent. If we're looking at bad programs, JS programs are famous for importing 15MB+ of code for simple functions.

While using a runtime written in C++.....

In a few years or so, the runtime itself will be in JS. It's unavoidable, this is the way things are.

Until JavaScript has the language features to be able to bootstrap itself, that won't happen.

As long as JS is jitted/interpreted at runtime, I don't even know how that would work!!

Correction: LXQt uses Openbox (not Qt) for windowing, and offers a choice between no compositor (by default) or one like picom (not Qt) or KWin (Qt Quick, JS-based, I wish it wasn't JS-based but it's too late to change that).

Qt Quick is not based on JS. JS is merely an option for Qt Quick.