> GNU bash is the most popular shell implementation in the world. It was first released in 1989, and implements the POSIX standard plus many extensions. It's the default shell on most Linux distributions, runs on BSD Unix variants, used to ship on Mac OS X, and runs on Windows.
Mac never stopped shipping Bash. What they did was to no longer use it as the default interactive shell. Zsh is now the new default shell. As far as I know, Mac has never shipped with Fish.
Default shell is zsh. They ship old version pre-GPL3 bash. I just “brew install bash” and then change my user shell in the system preferences to point at it.
Note that macOS still ships bash.