The true answer is that there is just some software that is antithetical to the philosophy of nix. It’s not necessarily nix’s fault that this is the case, but their purism towards resisting opaque binary blobs going into the store reflects on the actual state of what’s available in nix.
You need some impure, nonreproducible way of managing that software. So on nix Darwin I let these opaque binary blobs manage themselves via homebrew and use nix for every other case possible