In practice, it's not that restricting. It's pretty rare to find something actually requiring a more recent version. (And there's slow progress in updating it)

Randy Eckenrode is doing work pushing this forward almost every day, and constantly posting little updates on Matrix in the Nix on macOS channel. If anyone reading this is invested in that work, you can track it just by idling in the room. I'm sure he'd appreciate help or even just sincere expressions of encouragement or gratitude.

You can also sponsor the work https://opencollective.com/nix-macos

Granted, it’s not restrictive if you only want to use Nix for general utilities and Unix libraries. But it’s extremely restricting if you want to use Nix to manage macOS apps. And I love Nix, so of course I want to do that :)

Thanks for posting the link to sponsor this work.