Atom has actually gotten significantly faster recently. It seems they've started to rewrite some core components of it in C++ for performance reasons. I've also used some Electron apps that are very lean. I think it's more of an implementation issue. Slack is pretty terrible at resource usage, for example, but Zeit's Hyper is very efficient & it's resource usage is comparable to iTerm in my experience.

Slack's issues with their electron app shouldn't be particularly surprising, either, considering it was their head architect that published an article on Medium advocating for PHP on the basis of it's concurrency model...