I use Gnome 3.4 every day and would never go back to the old ways.
Extension are a terrific idea and there is plenty of development in that area. The future of the desktop is as a seamless connection to the Internet, so that local apps and online apps are both available as if they are all installed locally. Queue the naysayers who will go on about what happens when you do not have a connection. That is why Gnome can be a mixture of local and remote.
You can stay stuck in the past with Mate, or move into the future. It does not bother me if you stay stuck in the past, but I look forward to the next generation of Gnome, and the one after that.
Lastly, there would not be a Unity or a Cinnamon without Gnome. Both are merely alternate shells to Gnome 3.x. But that is the strength of the new Gnome, you can make alternate shells.