Pros don’t give gimp a chance but many of us still test try it. It’s not viable, not only because Adobe is a must have because of interoperability but because it’s faster to work in, it’s faster, more stable, more supported,… literally there is no category in which it was worse. Ux is not the best for sure, but it’s still way better than gimp. Even more, everything works in the same patterns as the users expect. Same as other graphical programs. It’s easier to use, easier to switch, easier to use similar software. That’s ux. Gimp doesn’t have that.
Because of all that, it doesn’t have a target audience beyond someone who is just very determined to use something free.