Many other projects are very competitive (or better) than commercial options but GIMP is not even close.
They just released support for 16bit/32bit/c color last year which is needed for so many scenarios.
The unified transform tool mentioned as a highlight is really a pretty simple thing to code.
They are 5-10 years behind what you get in PS for $10/month. It's a killer for any professional have tools that far behind their peers.
The UX has always been poor and unnecessarily complicated. I resent the implication it's the user's fault for not taking time to learn. There are many examples of complex professional systems that prove a decent UX is still possible.