> As far is I can tell this has (mostly) nothing to do with constrained resources and just with the extremely technical perspectives of the maintainers.

Discord, for example, has 450 full-time employees and is valued at $7 billion. I simply don't see how small non-profit teams, many of which are run primarily by volunteer labor, can compete with that in terms of UX. How many full-time designers or UX folks are working on GIMP or VLC?