GUI is not just your "overlapping windows" straw man, it's interactivity, plus graphical display. Yes via a taxonomy hack TUI is not GUI and there are technical hacks that bring graphics to TUIs these days, but the point remains that we need complex (but not overlapping windows, sure!) interactivity and rich display capability.

That is what we need, and if you're making the argument that a terminal shell is the best place to provide them then I don't know what to say.