I have a confession to make; I'm an inveterate worldbuilder. Creating, detailing, and now partially destroying my beloved collaborative homebrew of CITY has brought me a ridiculous amount of enjoyment over the past five (or is it six?) years. Now with advent of the new edition, we're hard at play again designing a new setting for our 4e campaign in the fall. The slightly-rotted-to-the-point-they're-alcoholic fruits of both labors are posted here.
I don't see a move away from DM's as world-builders. Like the poor, they will always be with us. Perhaps there's a move away from a certain kind of worldbuilding, or as is more likely, it's just a reaction to some vocal posters here trying to claim a particular kind of worldbuilding as definitive.
My approach is to build worlds to tell stories in, they only need to make as much rational sense as their source literature and films (heh). Their tides are driven mainly by plot-necessity. Their only currency is contrivance. What realism or sense of simulation they have gets slathered on, butter-like, over the top... often with a few slices of cheese...