but the "way way more web developers" you mention are not, at least in the context of electron apps, interested in that feature except tangentially..
so while everyone knows a full web-ready browser engine is impractical to design from scratch, maybe a simplified engine that supports a conservative subset of best-practices web-style design is in order?
The issue here is re-use - Sciter is small and very fast, but won’t run an arbitrary existing web app that targets Chrome. Maybe you could argue for a middler-ground, add more HTML features to Sciter until it can run “most” things… but you’ll end up back to having the whole banana.
Maybe something a bit opinionated, like a React Native-only runtime, could fit the bill here.
Or in a sense, is this what Flutter is?
The big draw for Electron is that we have way way way more web developers out there these days than native-code desktop UI developers, so it's easy to leverage those people and get results fairly quickly, even if the resulting apps don't really conform to any desktop's standard look-and-feel (which I guess avoids the uncanny valley effect of cross-platform toolkits that try to be native, but fail in subtle and not-so-subtle ways). People can even just (sorta) repackage their existing webapp, and end up with more or less a single code base for all desktop platforms + web.
I do agree with you that most of the desktop platforms are pretty annoying to develop for if you want a solid, stable base, but I don't think that's the prevailing reason for Electron's uptake.