> Emacs is written in Elisp which is a dynamic language just like JavaScript

All dynamic languages are not born equal when it comes to performance. 2 implementations of the same language aren't even equal. While V8 is a fast JS engine, the DOM isn't. Emacs doesn't rely on the DOM unlike Atom or VSCode.

emacs core is written in C. All of your extensions are mostly in elisp. A few run servers and talk to them though. (Eg ensime)