You know, I don't see why Arch and other distros couldn't have a declarative abstraction layer. You don't hsve to go full Nix or GUIX just to hsve that.
I used to think that you don’t need Nix to get most of the benefits that Nix/NixOS are known for. And to a certain extent, that’s true — you can achieve much in other scenarios. But by now, I think the reason why Nix/NixOS work well and deliver these powerful abstractions is because they are Nix all the way down, giving you an unparalleled level of integration/reach for your declarative layer.
Ansible at least doesn't lie to you about this: it provides the tools to be declarative, but doesn't pretend to understand your problems better then you.