I like it as a concept, but it gets bothersome to maintain on the long run, sometimes you just want to install something not write configs.

I think Gentoo has a nice middle ground, where you can install packages as a one-off without adding them to the world file, which makes it very meat to maintain both your regular packages and some random things you're trying out before settling in on adding them permanently.

That being said I'm currently looking into writing some ansible for kick-starting machines, so I'm very much moving in that direction. Why not use nix then? Few reasons:

• Using Nix means I'm forced to use Nix, whereas with Ansible I can use whichever distro I want, more than one even.
• I don't want to have to define EVERYTHING, I want to be able to bootstrap systems quickly, but after the initialization I want to be able to mold each system to what I need without worrying about making it reproducible.
• Nix uses a language that's only usable in Nix, in short I would need to study and learn something that's only usable on one specific distro.