This is a good point, but it would be interesting if we had a "just enough" rendering engine for UI elements that was a subset of a browser with enough functionality to provide a desktop app environment and that could be driven by the underlying application (or by the GUI, passing events to the underlying app).
Funny thing about all of this is that it's just such oppressive overkill.
Most GUI toolkits can do layout / graphics / fonts in a much simpler (and sane) way. "Reactive" layout is not a new concept.
HTML/CSS/JS is not an efficient or clean way to do layout in an application. It only exists to shoehorn UI layout into a rich text DOCUMENT format.
Can you imagine if Microsoft or Apple had insisted that GUI application layout be handled the way we do it today back in the 80s and 90s? Straight up C was easier to grok that this garbage we have today. The industry as a whole should be ashamed. It's not easier, it doesn't make things look better, and it wastes billions in developer time and user time, not to mention slowly making the oceans boil.
Every time I have to use a web-based application (which is most of the time nowadays), it infuriates me. The latency is atrocious. The UIs are slow. There's mysterious errors at least once or twice daily. WTF are we doing? When a Windows 95 application ran faster and was more responsive and more reliable than something written 30 years later, we have a serious problem.
Here's some advice: stop throwing your web code into Electron, and start using a cross-platform GUI toolkit. Use local files and/or sqlite databases for storage, and then sync to the cloud in the background. Voila, non-shit applications that stop wasting everybody's effing time.
If your only tool is a hammer, something, something, nails...
Problem there is Electron devs do it for convenience. That means esbuild, npm install react this that. If it ain't a full browser this won't work.