Given that FOSS developers are, in some sense, their own users, (a) and (c) are not always unjustified. For my personal use case for LibreOffice specifically,

Given that FOSS developers are, in some sense, their own users, (a) and (c) are not always unjustified. For my personal use case for LibreOffice specifically, I don't give a damn how ugly it is, and I'm willing to have some patience if it's a bit slow, but crashing or hanging on a 160-page document is unacceptable. So adding a designer to the project wouldn't add any value to me.