I do wonder about the "deliberately cryptic" nature of Nix's expression language. It is, in fact, deliberately designed for simplicity, to be a basic syntax for a language that is purely functional and lazy but not much else ([0] p69). When folks complain about the Nix expression language, as they often do, I ask them: What would you change? How would you do it?
I think that it is bad that an entire team does not have the bandwidth to learn an entirely new language, but good that the team is not willing to spend time on things which they don't think are important.
Not all technologies are good. Not all organisations are good. Sometimes it's one. Sometimes it's the other.
And sometimes it's neither; some organizations are perfectly competent at what they do, but for whatever reason are poorly suited to a particular technology that would work fine elsewhere. (Dumb example: a company overwhelmingly built with Microsoft technologies that only has expertise working with that particular stock has basically no chance of being a good fit for nixos)
Moreover, there are lots of folks having professional success with Nix, and having consumed enough of their stories, I think that the stumbling blocks that the parent identified are faults of their organization and not of Nix in particular. To see this, first replace "Nix" with "Brand X" and note that the complaints are generic to any community-developed software which doesn't have B2B resellers. Then, consider your own experience learning Nix, and note that usability, poor documentation, and a feeling that things are deliberately cryptic are all common to learning any new tool or programming language.
We can comfortably conclude that Nix did not prevent itself from being adopted by the parent's organization. Indeed, it would seem that Nix made itself extremely attractive and adoptable, else it would not have been under consideration!
As an example, I recall trying to build a package for psycopg2 (it wasn't in nixpkgs at the time, and even if it were, for one reason or another we couldn't directly use many packages from nixpkgs), the most popular Python library for interacting with a Postgres database; however, that required me to write packages for a bunch of C libraries that I didn't understand at all, including fishing random header files out of the Postgres source code. No one in our organization including our Nix veterans could figure out how to build it correctly, and it ultimately caused us to move away from Nix (it was among the last straws).
Besides, just because it didn't work for us doesn't imply that there's a problem with our personnel (by several industry key metrics, our devops capability is excellent), but rather that the effort required to implement Nix successfully was greater than the work required to use other tooling. We could use C++ instead of Python for our organization, but just because we don't doesn't imply that our organization is incompetent; rather that Python's tradeoffs are more appropriate for our problems. In effect, Nix creates more problems than it solves for us, which is unfortunate because the problems it solves are really important problems, and many of the problems it creates are utterly unnecessary (add docstrings, use a more familiar expression language--maybe Starlark [https://go.starlark.net], provide and document 'escape hatches' so users can use system dependencies where it's prohibitively difficult to hermetically package things, etc).
I maintain a few open source projects. I have made packages for Redhat, Ubuntu and Arch and updated one Nix package. I love the idea of Nix, but have quit trying to support it and have removed myself as a maintainer.
Places that use functional language for their code base don't have problems picking it up. It is especially big in Haskell community, because Haskell is also lazily evaluated.
People might wonder why not use language that more people are familiar? The reason for it is that purely functional and lazily evaluated language is basically behind Nix's biggest strengths. Purely functional means for the same inputs(architecture + source code + dependencies + configuration options + etc) you should get the same output, there's no mutable state the languages always starts the evaluations from a known state.
Why lazily evaluated? That makes the Nix only evaluate things that are necessary to obtain given derivation.
I think when people talk about Nix being confusing they really mean NixPkgs. Which is like a stdlib of Nix. The thing is that Nixpkgs in a constant flux people who work on it work on different components somewhat independently. Also often they realize better ways of doing things, and often the documentation doesn't keep with it. I think that Nix needs some kind of mechanism for literate programming where documentation would live together with the code and would be updated at the same time. There are some effort for example like the NixOS options page is generated from the source, but that's just just small part of Nix and only applies to NixOS.
I also would love if nix would standardize on how to pin nixpkgs. I recently discovered Niv[1] and it makes reproducible builds so much easier. I think Nix also needs some opinionated tooling to create dev environment for each supported languages, currently people need to do it themselves, and it takes a lot of research.
I think Niv + lorri + direnv make dev experience extremely enjoyable. For example a python project set up that way. Once you enter the directory, you have the exact version of Python installed that has all the dependencies (of course with locked versions) and all extra development tooling that developers need with exact same versions. All you need is just run the application and it just works every time. If somebody broke something you can easily use git bisect to find when and why it broke.
Nix fails to document though how a new user get to that point, and desperately needs help there.
I shouldn't have needed to do this anyway - the nix team should run a mirror for external URLs, except there's no way I see to tell nix to use a mirror without editing all the URLs to point there.
making mirroring bots or connectors to other package indexes, e.g. npm2nix, is a painful experience. it's also frustrating to have to inline bash scripts to build packages.
one of the things Guix got right that Nix didn't, IMO, was using a capable language where implementing these patterns is easy, and using guile scheme instead of bash to actually build the packages. a Guix-like OS with the breadth of nixpkgs would take over the world - I hope both projects can learn from each other.
