Terrible usability will be the right term, if someone suggests applying one type of UI to an inappropriate situation/user/task. Such suggestions sadly seem to happen a lot in the Linux space. And saying CLI is easier is a sweeping proclamation. Whereas I've avoided making sweeping proclamations, repeatedly describing the many cases where CLI is poor. Usability analysis needs to know about the user and the situation. It's not one size fits all.
I've used various command line systems a lot in the past.
I'm saying it's more productive for many to invest in extending learning their home environment than learning a completely unfamiliar and inappropriate environment.
Gimp isn't perfect. But neither is Photoshop. In fact Lightroom users grizzle that Photoshop is so much harder to use than Lightroom. It's a different animal.
I use Pinta or Paint.Net when I want a quick edit. But Gimp has the tools for serious editing. More tools, more hard to use.
Some Gimp things, yes! should be improved. And other things are being improved as we speak. And some things can be done on a photo much easier in Inkscape.
I hope the whiners donated to Gimp development? No? Then just please step back, and think for a bit. If thinking is too hard, then just take a deep breath.