mise kind of supports dependencies, just not in the way people expect coming from any other package manager. The dependencies in mise are not automatic and all of them need to be manually defined. They're to get around ordering issues since mise installs in parallel, e.g.: if you use "pipx:black" you need to wait for python to finish installing. (This is the "depends" option on tools")
This is intentional as mise is not intended to be a full bootstrapping solution in the way homebrew/nix is, mise is designed to be an overlay on top of existing systems. So if you want to manage python with brew and black with mise it basically just works without extra configuration. I think this design decision has paid off in spades. It sounds like a drawback but at the end of the day it's probably the #1 reason users find mise easy to use.
Thank you for making Mise!