Earlier quoted context omitted.
It basically does replace make/just, nix, direnv in one convenient binary. It’s very pleasant to use.
How is it more pleasant than the others? I've used make and nix, but not extensively. They seemed fine. Make seemed extremely powerful if a little rough on the edges at times. Nix was not super intuitive and I was never content with it before leaving it behind. That was probably a me-problem, because I could tell it was very capable and designed well in some ways.
I came from dealing with various node / ruby / python versions across multiple projects where I used nvim / rbenv and some python manager. Miss is nice as you can just switch to it and not relearn anything, it just works with the old configs.
I haven’t tried make with our setup but nix was too much of a hassle. Especially when some projects required old versions of libraries across dev (macOS) and staging/prod for various Linux OS.