That's pretty hyperbolic. It's not like GIMP doesn't have basic layers, blend modes, etc. And Krita seems to have better non-destructive editing than GIMP.
I don't think GIMP is going to blow Photoshop out of the water anytime soon, or is even too close to as competitive in its area as Blender is in 3D, but I've used Photoshop and Illustrator for maybe 50 hours and Photoshop wasn't drastically better than GIMP for basic stuff, composing a simple photoreal scene from individual photos, simple graphic design, etc.