If Apple as a whole is a disaster, then Tim Cook needs to be fired.

If Mac as a whole is a disaster, then whoever is responsible of that needs to be fired.

If Mac hardware is a disaster, then whoever is responsible of that needs to be fired.

If Mac software is a disaster, then whoever is responsible of that needs to be fired.

If Mac software UI design is a disaster, then whoever is responsible of that needs to be fired.

And of course the people above are responsible as well. But in this case there's a very obvious project which has failed.