They weren't really competing with Aero/Quartz, the most direct competition would be Android/iOS and the abomination known as WinRT. I don't know what happened

They weren't really competing with Aero/Quartz, the most direct competition would be Android/iOS and the abomination known as WinRT. I don't know what happened in 2010 or so, but it seems like all the GUI developers collectively decided to jump off the same cliff by gutting the desktop experience and trying to re-create it for tablets; never mind that there's still a whole bunch of people that would like to use a GUI on non-tablet devices.