The GUIs are nice, sometimes, especially for visual things. (Selecting an image, color, etc.) The terminal remains extremely powerful though in that it's much closer to the object, as it were. If you want to, say, change a setting on your personal machine, as long as the GUI designer thought that option should be included in the GUI (because including every possible setting gets very large and unwieldy very quickly) you're fine. But if you want to adjust that setting on 5, 10, 100 machines, that 30 second trip to the settings app turns into lots of work. If you want to set a setting that the GUI designer didn't decide to include, you're stuck. If you want to have an explanation of what you are doing, or what that other setting might do, terminal has man pages. GUI might have tooltips or a crowdsourced explanation.