One small shot with literally seconds of Screen Time can take months. The shots are much more complicated than ever before and the advent of CGI has just raised expectations from the Writers, Directors and Producers of what can be put into the final product.
The work on Star Wars was very simplistic in comparison and still took hundreds of people and thousands of man hours to accomplish. It does take less work than before, just as any improvement in productivity will, but it is far from easy.
Just an example. Our Friend was one of the guys working on the big scene in Serenity where a fleet of Military Space Ships followed the Firefly Ship out of a cosmic cloud. The scene was very impressive and lasted all of ten seconds. It took him over three months just to set it up. Tough work...
He has a couple of Emmy's from the Firefly and BG work. Now he is “between projects” and you can't eat an Emmy.
Serenity was a terrific movie, and was another of those heartbreaking examples of how the studios can completely blow the promotional strategy.
Like naming this movie simply “John Carter”, which means nothing to those not familiar with the books, the promotions and TV ads for Serenity told absolutely nothing about what the movie was about. The Browncoats turned out to see it of course, but people unfamiliar with the Firefly TV series were given no reason to go see it.