Could it be that these things are mutually exclusive?
Anecdotally, I've tried to learn Nix for several years. I learned to write Dockerfiles in hours.
Don't confuse expedience with usability.
Out of interest, what did you find difficult? I ask because I spent last weekend setting up NixOS, and the only things I found difficult were discoverability and documentation (I spent a lot of time just reading through the source code).
Edit: Thinking about it it's very possible that this is just a case of me not knowing what I don't know, since I'm not currently trying to do anything particularly complex.
The language is not too bad, but how it should be used is the missing part. Like a cookbook or a properly populated Stack Overflow site.
When I was on Linux, I liked to distro hop few times a year. Whenever I got back to NixOS, I felt that I had to relearn everything, and that there was nothing to grasp on to. I always take that as a bad smell.