To give a similar example: in the Rust programming language, dependencies are declared in a TOML file. While the dependencies are declarative, there's also a popular tool (that's being added to the main project) that lets you do
cargo add awesome-thing-rs
and add the dependency to your project, and edits the config file for you. That's it: no combinations to remember, no weird use cases, no unintuitive error messages, you just say "I want to add X" and then X is added.I don't see why Nix couldn't do the same.