From what I understand this would require an update to the Nix version that supports it... but that also potentially means bumping other environmental versions as well, which might not be desired. But I suppose this would amount to the user arranging the structure of their filesystem correctly so its one "system" per dir/folder... Or is there a better way to cater to this? And I suppose this still means that the node modules, gems, etc that are being used then anyway also need to be updated after this accordingly.
From my limited understanding of Nix, it seems interesting, and the article was actually useful to me. But I cant seem to shake the feeling that this is another packaging abstraction like others before it, and while it seems like a better variant, its not much different to having X, Y and Z listed as requirements and then letting the dev go off and install such dependencies on their system, in the way that they best know how. Juniors or those new to a specific environment might not know the ecosystem so well so as to know to use rbenv or nvm or whatever, but I'm not sure how Nix solves this issue differently than one of the specific tools its replacing.
Theres clearly more to Nix than just setting up language environments, which I'm guessing is where its usefuleness really kicks in. But purely for lang env set up, I'm not sure I see a point over other tooling...