In my experience a lot of these old projects really go out of their way to dissuade contributions anyway. Lots of naysaying "it's always been like that", ancient infrastructure - e.g. insisting on git send-email patches, etc.

Usually the only way it gets resolved is when someone writes a more modern competitor and it starts gaining traction. Suddenly all those improvements that people tried to do and were told were impossible and stupid aren't such a bad idea after all.

I don't think that's the case with Unity but it probably is with things like GCC, sudo, sysvinit, X11, etc.