Inkscape has had the same basic UI for about a decade. I just upgraded this week on my machines to 1.1.2 after using 0.96 for a long while, and I felt at home still. Inkscape's UI hasn't changed much because there's really no other UI for SVG stuff. Look at Adobe Illustrator and you'll see that modulo some very small differences, there's a lot of the same UI in the same place or nearly the same place.
What has seriously improved in Inkscape over the last decade is definitely performance. Every release, I see major perf improvements.
Blender and GIMP have both had major UI overhauls, but Blender has seen the largest. in 2019, Blender threw out their old UI and built a whole fresh one for 2.80. 2.80's UI absolutely brought it up to the same par that a lot of professional tools are at now.
I will also mention that Blender is being used __In Industry__. In 2019, Ubisoft began tossing money into the funding pool & is using it internally for their animation: https://www.blender.org/press/ubisoft-joins-blender-developm... & there's a few places it's been confirmed to be in use over in the Techways course on blender: https://techways.online/courses/blender/lessons/blender-basi...
But to your point about community: Something I had to learn long ago was that all projects, open source or not, push against "Change for Change's Sake." Several attempts had been made at updating Blender's overall look and feel but with mixed reception, even from within.
The best way to get something done in any part of a well established ecosystem is to rally some friends, get a good proof of concept working, and present it. This is how three major changes in Linux have been done: Lennart Poettering, as much as you might disagree with him, stood up and said "Sound on linux sucks because you have to do a bunch of ioctl shit. Let's make a good API and a sound server to go along with it so you get all the advantages of modern audio routing". He then stood up again and said "you know what, sysV init sucks too, let's make something that handles the configuration for the vast majority of the peripherals on a system and the services that depend on those peripherals."
The fact of the matter is that most Open Source is maintained in the spare time between meetings and shifts flipping burgers:
* Lots of FOSS projects are one person maintained, in their spare time, more and more by people working dead end hourly jobs like retail. Seriously.
* The big ones out of companies are probably maintained by zero people full time.