The Star Wars prequels (especially the latter two) are layered with so much CGI, it's almost impossible to see where any kind of practical visual effects are being used. And from what we've seen in various making of documentaries chronicling the Star Wars prequels, there were barely any practical effects used at all: everything was shot on a green screen, just 'cause. What was completely forgotten in favour of rendering environments with CGI, of course, was the genuine sense of wonder that a practical set can bring. You can actually feel them in your bones, whereas CGI feels generally cold and clinical. I'm not saying the movie shouldn't use any CGI - it definitely should (and definitely will), because this is the 21st century, and J.J. Abrams is directing. But practical sets are absolutely necessary if Disney want to bring faith back to Star Wars fans. They want to take a nose dive into a galaxy far, far away that feels real and lovingly constructed.