I would argue that Nix does not make trivial environment setup easy. One of the reasons I love Flox for my own development is that I can just "flox install" packages. That doesn’t really exist for project-specific packages with Nix ("nix profile install" exists, but that installs globally). I would say give Flox a try and see if you actually run into issues. If you do, we're pretty good about fixing them as they come up.

It has also not been my experience at all that Nix packages are "often unmaintained and simply broken." I use Nix every day for work, and I use it to configure all of my personal machines (on both macOS NixOS). Can't say that's ever really been a problem for me.