Outside Nix, there's Brioche (my project!), and there's also Vorpal and Tangram, all of which are "Nix-like" but are from-scratch projects instead of using any Nix tooling
So I definitely agree that Nix as an _idea_ is right, and I definitely also agree that NixLang is a blocker for mass adoption. Personally though, I think if you dig deeper, there are other places that could use improvement beyond just the language itself (but nothing that would necessarily be a show-stopper for adoption IMO). But that's why my project is a "Nix-like"-- there are things that I think Nix could / should do, but which aren't really compatible with the way Nix itself works. One example: Brioche works without having a global store path-- it's per-user instead so that it can be installed rootlessly-- which doesn't really map well to how Nix itself handles store paths and dependencies
So point is, I agree Nix is the right model, but I think the _real_ gold lies outside Nix itself (...with the side note that I'm obviously biased!)