@publicvoit I'm an ex NixOS user, and I'm using GuixOS now. Migrating a working setup to another system is usually a joy in #NixOS and #GuixOS. Also studying the setup of others, and copy and paste good idea. But I agree that creating this "magic" working setup can sometime be a pain.
Moreover, if an application is also a platform, supporting plugins like Emacs, KDE, or IDE like Jetbrains, then it cannot work correctly in a Nix/Guix OS environment, because it is not running in a Filesystem-Hierarchy-Standard, and ideally also the plugins should be ported to Nix/Guix.
Summing up: what works, works very well, since it's reproducible and all in a few files (as reported by @eliasp ), but what doesn't work can be very difficult to port to Nix/Guix (as reported by @publicvoit).