> Nix is not a drop in replacement for homebrew, nor is it fast when it comes to community updates.
I am certain there are some exceptions and edge cases to this, but in my experience nixpkgs is the largest and most up-to-date repository of all, by a wide margin. Did you use nixpkgs-unstable or a stable release?
While I am a happy user of Nix and think that the unstable channel is generally recent enough, I have not quite found it to be the "most up-to-date". Among the package repositories I have used, that honor probably goes to openSUSE Tumbleweed.
I am certain there are some exceptions and edge cases to this, but in my experience nixpkgs is the largest and most up-to-date repository of all, by a wide margin. Did you use nixpkgs-unstable or a stable release?