I believe customization pretty much moved focus away from MacOS. I personally have changed the look of Vista to something i like, picking up ideas from different sources, and not going for an actual Mac look, thus leaving the necessity of MacOS emulation resources out of the game.
See this ss:
I have RK launcher, Rainmeter, FineXer, QTTabBar, EmergeDesktop, and WB running @ 25% RAM (goes to 19% when not running apps). And is pretty much what i want it to be. I guess most customizers dont really care about getting the Mac look if you can get a Mac instead nowadays and they go for a p