It's funny to hear that, because we get a large number of complaints that we haven't changed GIMP's interface at all from 2.10 to 3.0 and that's why we're "failing".
We try to be respectful of existing users (and again, we get lots of complaints that doing so "holds GIMP back"). If you have some examples of massive changes you've dealt with (and from what version to what version), I'm happy to look into them further.
I think if Blender can do UI change, GIMP should too.
Please finally implement pie menus, like Blender has had for many years. There have been various pie menu implementations for GTK for decades, and it's always been easy to roll your own if you suffer from NIH so much that you refuse to look at or use anything anyone else has ever done.
I believe GIMP's deep seated NIH syndrome, and refusal to look at or acknowledge anything else, and lack of respect for users' requests and usability itself, are GIMP's actual deep seated problems (which the Blender project so successfully doesn't self-sabotage itself with), and I have no reason to believe it's ever going to change, because it's so deeply baked into the GIMP "culture", if you can call it that.
Photoshop doesn't have pie menus, so if you must, think of pie menus as a way to be even less like Photoshop, if that is what mission drives you instead of usability. But I think your design goals and motivations should focus more on usability and supporting users than simply spiting Photoshop.
But once you finally get tired of spiting Photoshop at the expense of usability, then why don't you finally declare Mission Accomplished, and move on to trying for once to be as good as Blender's user interface and responsiveness to user's needs?
https://news.ycombinator.com/item?id=43491589
>One example is that Blender embraced the use of pie menus, and Gimp ignored them. The Gimp team is just not open to outside ideas, and gets really annoyed when users of other tools request features from those tools that Gimp refuses to support, and reacts by digging in deeper and clinging to their bad design decisions out of frustration and spite. A really sad culture of NIH and 4Q2.
>In general and with many other things, Gimp could have been so much better and easier to use, but they systematically and spitefully ignored their user's needs and requests about so many things, while Blender did just the opposite, listened to users and improve the user interface and mouse bindings, instead of being stubborn and parochial about it. [...]
https://news.ycombinator.com/item?id=38236366
>[...] All of these ideas could be applied to Gimp too, of course, but I've found the Blender developers to be much more open to entertaining other people's ideas and contributions about user interface design than the Gimp developers, who have been historically NIH-limited and stubborn (especially about changing the name to something less offensive to the general public). At least Blender already supports pie menus well, and changed the default mouse bindings in response to user demand, and has made huge strides in usability lately. At this point I think it would be much easier to just add a great image editor to Blender, integrated with its video editor, than try to change the minds of the Gimp developers. [...]
Maybe my angst is from prior versions. I've been using it since... well, it has existed.