We're talking about an interface thats acceptable to the masses. I'll bet that statistically more people use Aqua on a constant basis than any other theme (barring Aqua variants). Obviously not all teamwork yields great results, and certainly designers didn't decide the functionality of OS X itself. You cite the Aztek, when in fact teams of designers have come up with countless other fantastic designs. Personally I think the Aztek looks rushed, like someone just mass produced a prototype, but thats another thread. True enough, some lone designers make great stuff. Its just not always pleasing to everyone. Designers work towards perfection, when in the case of Aqua they had to work towards something widely acceptable. Surely Aqua is overdue for a make-over but it has certainly set a standard, one that even PC weenies want.

There is one way in which Apple could appease everyone. Simply make theme impossible for third-parties to make while creating a couple of other interface options tucked in the General prefs, such as window borders, a smaller gui (Aqua elements are huge) and a few carefully designed themes. Hell, even throw in an option to have the menubar on application windows instead of atop the screen. It would make OS X truly one of the most adaptive GUI's.