My issue with Guix coming from NixOS is the missing first-class zfs support for root, crypto included, RustDesk, few other common services who are hard to package.

Guix potential target IMVHO should be desktop power users, not HPC, NixOS while mostly developed for embedded systems (Anduril) or servers in general still take care of desktops, Guix apparently not and that's a big issue... Nowadays outside academia I doubt there are many GNU/Linux users who deploy on plain ext4...