Good electron replacement should re-use your installed browser engine. That would reduce RAM consumption dramatically, while providing better security (because browsers usually update faster than individual apps).
Developers don't use electron because it'll get its own browser engine instance.
If you can't, it's not the browser's fault. I can definitely screen share in Jitsi from the browser, so there's no technical reason Slack shouldn't be able to do the same thing.
One is that TLS is married to DNS, and no third-party CA would issue a certificate for localhost. TlS with self-signed certs generated on the spot becomes easy to forge.
Another is that no web browser suppoorts Unix domain sockets or a Windows equivalent as a an access protocol. You are stuck with IP-based access, wee above.
Third is that access to the OS is limited or forbidden inside the browser, for a good reason. Want to run a locally installed compiler from within your web IDE? Tough luck.
Electron solves all of these problems. It doesn't do it in the best way imaginable, but in some cases just a web site cannot be a replacement.
I also see this project but you have to write Go to talk to the OS, not Node: https://github.com/zserge/lorca
But if you want broad cross-platform support "just get the locally installed browser engine" suddenly becomes a hard problem, unless this becomes a popular OS feature.
At the same time, companies were locking down WScript due to scripting viruses and HTAs that were impersonating other applications with their configrable icons.