I know this because I am a developer and have a very good designer friend.
Or maybe UX as a separate role only works in hierarchical organisations where you only have to convince a few people that maybe don't care that much, don't have to do the work themselves, and might not enjoy thinking out things on their own, just saying...
You do know that we, the GNOME application developers, spend a lot of time supporting both MATE and unity to give people the best experience no matter which shell they use, right? Do you feel excluded by our work?
And with current technologies I'm sure you could set it up to be all remote with volunteers who'd like to help or use the help of their family members.
Find 2 or 3 random people and ask them to do some task while describing their thought process. Get your devs to watch the recording, notice what's not easy to understand in their UI and make it a priority to resolve.