I believe for a developer tool to success, for the most common thing to do there has to be at least three ways an engineer may misuse your tool and still get it "done" (by leaving non-obvious tech debts behind).
This is true for git, but not so true yet for Nix, so I'm not sure a GitHub-like moment helps.
In a full-metal-jacket NixOS setting it’s bloody hard to bash (no pun intended) your way through to the next screen by leaving behind tech debt (Python comes to mind, I made the mistake of trying to use Nix to manage Python once, never again).
But anywhere else you just brew/apt/rpm install whatever and nix develop —impure, which is easier than most intermediate git stuff and plenty of beginner stuff. git and Nix are almost the same data structure if you start poking around in .git or /nix/store, I might not understand what you mean without examples.
But all my guesses about what you might mean are addressed well by flox.
This is true for git, but not so true yet for Nix, so I'm not sure a GitHub-like moment helps.