I feel like nix has been thoroughly discussed in this post already, so you're not the only guy.

> You don't need to mess around with shell hacks

Shell integration is optional, you can use `mise en` just like `nix-shell` or `nix develop`. You could also just invoke commands/scripts through mise tasks or mise exec.

> based on a string in one of several dozen dotfiles

The "Idiomatic" files like .nvmrc, .python-version, etc are supported but most people just use a mise.toml, which (a bit like flake files) contains all the config for the environment.

> but when tools are published through NPM or RubyGems or Crates or just on github that you have to run `go install` to get, then it's a bit of faff

And this is what mise excels at: `mise use npm:cowsay` or `mise use ubi:junegunn/fzf`

I think Nix/Guix are great, but also terrible. For me today, it's not worth the pain.