I would like to make a guess and say that the stagnancy of jQuery UI has a lot to do with jQuery Mobile (which if I'm not incorrect actually is a child-project of jQuery UI). I do however agree, jQuery UI is in many ways awesome, but needs to pick up speed.
I just had to agree with this comment - Finder might just be one of the worst parts of OSX. In my opinion the Ribbon UI may be one of the biggest innovations in UI Microsoft did during the 00's (Metro UI = 10's?). The amount of space that the Ribbon UI provides for the main window (way more rows than the old UI) and the few amounts of clicks needed to perform your actions make it crazy efficient!