The greatest failing GIMP had (and still does) is that has almost nothing in common with Photoshop UI-wise - or numerous other photo editing tools. I've used them all my life and every time I open GIMP, I can't seem to do anything.

It's like walking into a car dealership and they tell you their car is free, and you ask where the seats are, and they say "why, on the ceiling, of course. We didn't want to copy all those other car companies."

You pop open the hood and there's no engine. "Where is the engine?" "On the roof!"

"Where is the gas tank?" "It's that plastic bag you keep on your lap."