> People have complained for years that their UI is too complicated

Isn't this a feature?

No. If a tool is too complicated or cumbersome to use then people will look for another one that’s better. Not everyone is an enthusiast that is willing to invest hours or weeks learning all the intricacies of an app if all I want to do is some light editing of a photo or very simple illustration drawing. I will choose a tool with better UX and easier workflow 100% of the time, and most people are like this.

So maybe the target audience isn't most people? I get that people like things to be simple, but some people love the depth of GiMP is a feature, not a bug.

I used to be a staunch critic of GIMP, recommend everyone use Krita instead and so on. But recently I've given the new 3.0 version a go and... it's quite an improvement if you adjust the time scales to decades rather than years. I've used GIMP first in 2000 (it was actually my fist "real" image editor, other than stuff like paintbrush) and a LOT of the finicky stuff has been removed or improved since then. Having do deal with per layer canvas boundaries? gone. Having a floating "ghost" layer whenever you made an operation and having to figure out how to merge that back? gone. Need to work with mask and group layers? You can do it, and it doesn't give a brain aneurysm trying to use anymore. You can even apply non destructive filters and whatnot to the group layers!

Having the UI spaghetti all over the screen because it's just a bunch of loose windows? the default is just a single window with panes. Want to condense that mess of tool icons into a single column of icons? you can do that! In fact, you can reorganize the UI in such a way that it's actually not that offensive (please GIMP devs, have better UI defaults!). Even tough it has a GEGL operation for non destructive filters I think that's just a holdover from how things were implemented initially because most of the "normal" and "color" filters are already non-destructive and operate (from the user point of view) just like the GEGL ones. They might have plans to further convert all other destructive filters and merge the GEGL operation ones into the normal filters, hopefully soon.

Oh and by the way, you can certainly push GIMP hard nowadays. I've been doing some testing editing a 32 float bpc (128 bpp!) 16K image with a bunch of crazy non-destructive filters stacked and it handled it like a champ with a few slowdowns here and there, and my 32 thread ryzen CPU was at times fully maxed (yay for multi threading) and the RAM management was quite impressive with things using up to ~50GB of memory (you do have to configure it let it use all that) and no memory leakages afaik, closing just the file and reopening again worked fine. Also, zero crashes! Can't say the same when pushing Krita hard. It's quite smooth compared to how things used to be.

Honestly the potential is all there, I just hope that the GIMP devs get a break from all the negativity they've been receiving since... time immemorial and perhaps the rate at which they can improve their software increases now with all the inglorious refactoring work they've been doing behind the scenes being done.