Spotify is a good example of an application that doesn't use Electron (though it uses a similar framework) and still manages to be incredibly slow and bloated. As are most websites. So the problem might not be that Electron is slow... it might just be that the web in general is really slow unless you work extra hard.
And it's still significantly slower than something like Emacs or Sublime (or, dare I say, IntelliJ?). I like, and use, Visual Studio code but it's hardly performant.