Macros and symbols (even though he technically has Symbols) come to mind as indispensable aspects of elisp which cannot be replicated in JavaScript. Ignoring the fact that Emacs predates JavaScript significantly of course.
You are mentioned in the essay that contains the article in this HN post btw :)
Check out the Neovim section in https://www.murilopereira.com/how-to-open-a-file-in-emacs/#t...
A lot of the pain regarding JS build-systems could be avoided with macros (and reader macros/a customizable reader). Babel is literally macros + a reader.