YMMV, I don’t run a home lab, I just have a NAS and run a personal website. I definitely don’t have a “fleet”. I have two servers running Debian and I can bring them back up from zero in “Rebuild everything in one command and have it work” is not something that I’m chasing after and I am skeptical that it would work anyway. Maybe there is something I’m missing, but when I update the software, the updates come with changes and it’s possible that things break. My goals are to keep reasonably up to date and to be able to fix things quickly if they do break.
Regarding Nix complaints:
Package maintenance is kind of a crapshoot. Maybe your package is in nixpkgs, maybe there is a flake for it, maybe you find something that is actively updated, maybe not. Maybe there is a package but half the features are turned off because the maintainer didn’t bother. Maybe there is a package but half the features are turned off on macOS for unknown reasons. What I want is just to know what level of distro-level maintenance the package has, including its transitive dependencies.
Docs are just kinda bad. Fragmented across different sites. Docs teaching you Nix forwards or backwards, or teaching old Nix, or teaching Nix with flakes, or teaching you Nix for end-users or developers or package maintainers, or Nix on Mac or NixOS. A surprising number of broken links. What I want is one site, with a little drop-down menu to select the version I am using. What I have is hours spent on the NixOS Discord trying to figure out how to do basic stuff.