Unless you are attempting advanced things you don't need to know a lot about the language and how the more advanced things work.

Imo the harder part is learning bespoke build processes that you may not own in order to get software that assumes it can perform arbitrary network access or other naughtiness at build time to build successfully in a restricted sandbox.

The language is maybe a little strange at first but there's really not much to it.

Just find a project written in the same language that is already packaged and copy it, modify the name, version, source url, hash and that’s it.

It is one thing that is easier done from the top, instead from the bottom.

You don't have to know how to write Nix to write 95% of all Nix, it's just "JSON with functions" after all. There are definitely advanced things that the Nix and NixOS developers maintain for me.

Just like I don't know how to implement any crypto, or how to implement efficient 3D pathfinding I don't know how to implement NixOS. But I can write a derivation using the helper functions for the language I want to package, which aren't many these days since nixpkgs is huge already.