There's already a bunch of comments about Nix, so I don't want to repeat them, but really Nix is less complex than a handcrafted series of Makefiles, and significantly more versatile.

With home-manager I have the same packages, same versions, same configuration, across macOS, NixOS, Amazon Linux, Debian/Ubuntu... That made me completely abandon ansible to manage my homelab/vms.

Also adding flake.nix+direnv on a per project basis is just magical; I don't want to think how much time I would have wasted otherwise battling library versioning, linking failures, etc.