Most nix users still use brew for casks on mac. Using brew bundle as your interface to it makes things almost seamless, so its not too icky overall.

eg I manage my Brewfile declaratively with home-manager, and then run this on file change

        HOMEBREW_NO_UPDATE_REPORT_NEW=1 HOMEBREW_NO_AUTO_UPDATE=1 brew bundle --file="$HOME/Brewfile" --cleanup --no-upgrade