For me, JS+HTML+CSS isn't (I had to outsource most of the UI code to our webdevs), but Qt or GTK (or, god forbid, Cocoa and whatever is Microsoft's newest fetish) are so much less productive that I just cannot justify writing in it any more. If you want a smooth UX with things like animated scene transitions (people scoff at animations, but if used sparingly and at the right places, they improve usability), or just any non-standard widgets, it's far, far easier to do everything in HTML.
And the beauty of Electron is that you can still write all your actual logic in C/C++ and use Node's FFI to bind it to your UI.
(Qt is transitioning to the same model with its HTML+JS based Qt Quick orchestrated from native code; but it's far less production ready than Electron right now.)
The type of developer that only knows one language of any kind is in the same boat. Electron is popular because folks can write products at a faster pace than they could in other toolkits and languages. Being unproductive and fighting your tooling is not a sign of competency, nor is it a rite of passage. If folks can write apps faster in Java or Rust (which I love writing, by the way), I'm sure Electron would not have the adoption curve it does. Nothing to do with only knowing one language.
And the beauty of Electron is that you can still write all your actual logic in C/C++ and use Node's FFI to bind it to your UI.
(Qt is transitioning to the same model with its HTML+JS based Qt Quick orchestrated from native code; but it's far less production ready than Electron right now.)