The problem I believe is not with the startup time. If you load bunch of scripts in your emacs, it also gets sluggish at start. The way Emacs people solved this problem was to use a server client architecture and run Emacs as a daemon.

I think the real problem Electron apps face is that rendering everything on the DOM is really expensive. I still remember the VS Code bug that caused a huge battery consumption because the gif they used to display the blinking cursor was in a high resolution.

Emacs was critisized, heck even banned from uni labs back in the day, because it used too much RAM. Now the time has come for us to mock Electron based editors :).