Your experience and many other comments (as well as my own impression of getting into nix) make it look like there is a sentiment of removing nix-env from the documentation. There was a valid point in the other thread, that without either root access or home-manager, nix-env is the only way to get stuff installed permanently. I also repeatedly observed people rooting for home-manager to become part of nixpkgs or at least the blessed userspace configuration tool.
I would like this conceptual homogeneity: nix should always be used declaratively, for the system (NixOS) and optionally for the unprivileged user (home-manager). I don’t think it is worthwhile or even beneficial to integrate anything into each other. Just improving the documentation to lead people to home-manager directly, would prevent the kind of confusion and disappointment about the maturity of NixOS I had when reading the infamous wiki or third parties something along the lines of „Do nix-env, if you think that’s stupid, well, there is home-manager or something else, but then you’re on your own“.
So yes, I prefer to bless home-manager, as this appears to be the most efficient thing to do.
: OT: nix is exactly the tool to enables decoupling and separation of responsibility. I always found it weird how mind-bogglingly large the officially supported package set is. Why not have people take care of language ecosystems, areas of interest, complex individual packages, etc. on their own, and let them base their integration efforts on stable releases with strong compatibility guarantees within a release branch? Then one could either endorse usage of those third party collections in the documentation (and eventually systematically, by including package or option search results transparently for example) - or just let the ecosystem manage itself, people will have to evaluate what is alive enough to rely on anyway. NixOS would be a platform, not a planet-sized agglomeration of packages with too few people to handle them all.