When I can "pipe" the output from one component within a GUI program to another (of which there have been a few interesting research ventures), or even from one GUI program to another, and also automate this whole process with things like loops and conditionals on a whim (not just from scripts stored in files, but invented on the spot as needed) without resorting to writing a plugin to a program-specific API, then we will be on the same page.
GUIs don't have as useful of a REPL, but this could be fixed. GUIs don't have a programmable shell[1] that provides the conditionals and loops needed for automation, but this could be fixed.
Just post it to Hacker News when it is fixed!
[1] edit - Well, myself and others run stumpWM; which, being Common Lisp based, does provide a bit of a programmable shell and REPL, but this is not the norm for KDE, Gnome, etc.
Also, I think that most of the work that people do, even programmers, is spent doing simple tasks. The median shell command is more like a `cd` rather than a triple-piped command. So use GUIs for the common tasks, and when you need something more complex, use the CLI.
The general point is that I'm pitting the very best GUIs against the very best CLIs.