Nix the package manager uses the Nix language, and NixOS is a distro built on top of it. They’re all part of the same topic, and the article was talking about that.
You don’t get to decide what too much JS in the project is unless you actually work on and have in depth knowledge of the project. I dont like JS, but it has its uses.
Many people are conflating modern electron bloatware with ‘JS bad’, but things are not that simple.
Using JavaScript isn’t inherently a bad thing. JavaScript can be very useful when used for scripting. Obviously anything with a new for performance will be done in C.
The hardest part will probably be the installation, but if you can follow a youtube guide you’ll be fine. Go for a distro like PopOS or Fedora that have polished out of the box experiences.