Encouragingly, as well, the Guix package collection is growing at an exponential rate (as is Nixpkgs). In a few years there'll be twice as many packages or more, so if you can make it work now, it won't be tough to stick with it.
I've been using lisp for over 20 years now and would much prefer if guile replaced the nix language (or Common Lisp, if I can dream), but I still use NixOS for practical reasons.
But something I haven't understood is that nix compiles to derivations. I don't think it would be difficult to have a nix compiler that takes Lisp or whatever and spits out derivations. It would be able to use stuff from nixpkgs as well, at least partially anyway.
The built derivations are an extremely simple format anything can produce.
This is originally how Guix worked— it generated .drv files in the same format as Nix and then asked a Nix daemon to build them. But both projects consider the derivation format an implementation detail that should be free for them to change according to the needs of the rest of the stack, rather than a stable interface for downstream consumers (be they end users or other software tools).
The above is not just theoretical— as a result, the derivation formats of the two projects have diverged.
(Tbh I agree with their position, though. I don't think the concept of the derivation should really be visible to end users. The way the term is used is extremely overloaded/ambiguous, and so at the end of the day it's jargon that serves more to obscure than to teach.)
For reference Guix has 21,798 packages while Nix has 80,000+.
I think another issue with Guix is that some packages just seem to go away after a while, and it's a tiny bit inconvenient to get at older versions once they've slipped out:
https://unix.stackexchange.com/questions/698811/in-guix-how-...
That said I'm all for guix over nix (though day to day I use neither) because I think a full programming language is the better tool for this use case (in my mind terraform vs pulumi all over again).
Also there's one more issue which is related to guix's avoidance of binary blobs -- IIRC this means stuff like gfx drivers can be hard to come by/make work and I think this is by design.
Before that just meant that gamers maybe were left out (they weren't really the focus anyway), but now it might leave out a whole bunch of AI enthusiasts as well.