I don't remember exactly the problem since it was a couple years ago. There was a lot of issues in regards to failing to run / build rails which regarded doing special nix stuff to fix. It wasn't possible to include a custom gem from a separate directory. I had to disable some sort of sandboxing to prevent Nix from complaining. Nix kept getting in my way and as my team members were not familiar with Nix they couldn't fix it themselves. Sadly, I ruined their opinion of Nix by showing them it with this project.

There are no fundamentals hurdles, but because we are currently prevented from properly dogfooding these tools in Nixpkgs, they tend to be unpolished in various ways, they are just used to by a few random projects in relative isolation.