What do you mean by "richer ecosystem"? Have you ever seen GitHub language stats - there's so much Elisp on GitHub alone, it's absolute bananas. The amount of Elisp in the wild probably surpasses the amount of Clojure, CL and Racket combined. And mind that it isn't "a general use" PL - it exists for one and single purpose.

Lem is great and I'm happy there's finally something out there to challenge Emacs' hegemony, yet pragmatically, unless someone builds a way to run Elisp in Lem, it's unlikely to overthrow Emacs anytime soon, and that's just not gonna happen.

Org-mode, Magit, and thousands of packages aren't just "Elisp code" - they depend on Emacs' specific buffer model, text properties, overlays, markers, the display engine, process handling, and countless quirks packages rely on (intentionally or not). A Lem Elisp interpreter that didn't also reimplement all of that faithfully would run trivial `.el` files and choke on anything real. At that point you've reimplemented Emacs inside Lem.

Elisp is not the biggest point here and Neovim proves that with pivoting to Lua; the crux is the runtime and the corpus, and reimplementing those is the actual mountain. That is real ecosystem for whatever reason you're choosing to simply ignore.

Having CommonLisp as the extension language would indeed be a great improvement over Elisp.

However, I am suspicious about the dependency of Lem on Webkit, which for me is rather associated with inefficiency and low performance than with the instant reactions that I expect from programming text editors, terminal emulators and tiled window managers.

The main problem is that it is very difficult for any replacement of Emacs to offer everything that already exists for Emacs.

In my opinion, the only way in which such a replacement would succeed would be if it would include an automatic translator from Elisp to CommonLisp scripts executable by it, with equivalent functionality.

I chose the JS ecosystem. Why does the power of Emacs not belong in the browser? These days JS is a powerful enough FP language to do it.

"Common Lisp Emacs" has been attempted a few times. Lem seems like the best effort yet, and I was really excited about it until they decided to adopt a webview renderer.

I've got vscode for that.

I am not sure if I would bet one way or another on who has the richer ecosystem here.. They are both great. I would probably wager elpa has more packages in general than quicklisp, but maybe not necessarily richer/higher quality.