That's good to hear (and I think I heard about it before). The problem is, there are still lingering issues with Nix, like how long it takes to figure out how to compile a new program, (exceptionally) poor documentation, packages being unmaintained, the nixpkgs repository being a gigantic blackhole that takes forever to eval, etc.
Don't get me wrong. I really like the idea behind Nix. Even with this fix though, I'm still not sure I would enjoy using Nix (since many, many other problems) or giving it another shot because of my emotional response to it that's been caused by burnout trying to wrangle with it.
I'm not sure you would, either, and I won't ask you to give it another shot right now. I understand the feeling. Maybe it's something to revisit after more time than has already passed.
This is a common (and horrible) issue with dynamic languages that pass functions or blocks of code around. There have been some major improvements to Nix error messages which were included in the last release, and there's also ongoing work to address this through gradual typing.
There was a talk on the latter recently, with some examples that I think make the overall issue pretty clear: https://www.youtube.com/watch?v=B0J-SclpRYE