(I love this topic as well, and its title sums it all :P)

I think that you can rely on vi being available whenever you use an OS that claims to be "POSIX compliant", and that's why today I consider the ability to "save & quit" in vi one of the basic skills of any linux sysadmin.
Also, vi is some minimal stuff! As you praise graphical interfaces so much, I can't believe you'd vote for ed as the defacto standard for text editing.

I like your idea about the computer built around its graphical interface, and I must admit that I love how plan9 managed to make it's "graphical" interface (read "mouse usage") interface so well and be so efficient against the system.
Still, you interface with the system in text mode, and you don't "need" the mouse to actually make it work.

Imagine a system where you would NEED to be in graphical mode to update the system. That would be impossible to automate it properly... What if you had to flip a switch with the mouse, or click a button to restart a process whenever you edit a config file? That'd be painful...

Also, running remote GUI admin console remotely over ssh has been a thing for years, I guess people simply got used to the CLI ;)