For comparison, Windows 95's install package took up 19MB of disk space. So I guess Electron's 50MB is pretty efficient as far as operating systems go.
.NET does this, Java does this, DirectX does this, etc.
I think that's the point that they're making: Electron, due to its nature, isn't an optimal choice to build something that ought to be a small tool.
This is obviously a kind of "hello world" learning experience for you, and I'm sure it'll be a useful stepping stone to work toward more complex programs that provide better justification for the footprint. And with that purpose in mind, it's a nice start. I personally don't care for some of the UI paradigms that are fashionable right now (the "flat" and "minimal" stuff), but this seems like a sane implementation of that style.