I agree. GUIs are hard!
On the other hand, it seems like Open Source has a lack of designers that are willing to contribute. For example, in Tantacrul's critique of MuseScore [0], there's issues highlighted that seem obvious in retrospect, but in Open Source projects, unless there's someone who drives the user experience, it's easy to miss all these small things that add up to signal (whether rightly or wrongly is besides the point) a lack of polish.