To be fair on a modern setup it is fast. Sure it's not nano or vi(m) but compared to Electron-based stuff, it's plenty fast.

Five years ago:

    time emacs -Q -eval '(kill-emacs)'

would be slow at 320 ms.

But on a "recent" AMD 7700X that'd be 80ms.

That's starting emacs, evaluating elisp code, and exiting Emacs.

Surely if you can start Emacs, execute elisp, code and exit in 80ms it shouldn't lag too much to insert a character.

Now, I know, some modes can be slow. But Emacs in recent version as seen lots of changes enhancing its performances. And hardware have become really very fast.

YMMV but my Emacs is really incredibly responsive.

P.S: I was already using Emacs on a 486 back in the "Eight Megabytes And Constantly Swapping" days. The joke was fun and true. Nowadays Emacs is actually one of the lightest sofware I use.