Yes and no. The big advantage of a GUI is having interactive 2D coordinate input support (aka a pointer, or gestures.) While I think a keyboard can be a great control surface, that’s one thing it really lacks and only GUIs really offer. So to enforce that the whole GUI must be keyboard-drivable requires limiting the major advantage of the GUI. I’m a fan of the Emacs or Plan9 styles where the keyboard and pointer are able to be used together synergistically. You also see some of this in tools like video, DAW, and 2D/3D graphical scene editors.