Keep in mind that this setup is a one-time cost. Also, a lot of the code is related to configuring it the way the author wants it (via Home Manager).
Generally speaking, once you have a working NixOS config, incremental changes become extremely trivial, safe, and easy to rollback.
To provide another data point: I too use NixOS and oh boy that one-time is really costly. And while we're sharing Nix stuff for LLMs there's this piece of kit too: https://github.com/YPares/rigup.nix
Agreed, the learning curve is insane and docs are sparse. But it is truly worth it imo, even if you’re just using Nix as a build tool, or using Home Manager on Linux or macOS.