> But the official nix project has excellent documentation.
If it does, it's really well hidden. Because the nix manual certainly is not that.
> I think the problem is that nix is just hard to learn.
No, the problem is that nix offers no guidance or real help along that path. You go to https://nixos.org/learn.html and you've got essentially nothing helpful beyond the installation (which is easy enough). And it gets really bad when you get there from https://nixos.org/explore.html with no prior knowledge.
> Though Haskell folks eat it right up... no surprise there.
They're used to having to power through absent documentation?
I think the problem is that nix is just hard to learn. It's really different from most package managers, but people expect to look at a few examples and just pick it up intuitively. It's a whole different paradigm, with a custom programming language that also has a different paradigm. (Though Haskell folks eat it right up... no surprise there.)
It's gonna take time and effort to learn it, and there's just no way around it.