Abrams kinda fooled people with that, or maybe - as one of my VFX friends was claiming yesterday - he's just proven once and for all that most of the audience see what they expect to see or are told to watch for.

It's true enough that there was a larger percentage of sets used, and much less full CGI aliens and creatures than in AOTC and ROTS (TPM had less than some believe - even Lucas had a lot of doubts that ILM would pull them off convincingly and he played safe).

That said, TFA is also full of CGI. Set extensions, background matte paintings, visual enhancements, vehicles, crowd effects, particle effects, space sequences, CG doubles instead of using stuntmen etc. It's everywhere, in most shots. A friend who worked on the movie told me the # of shots with CGI in TFA is roughly equivalent to the number for TPM (which is less than for AOTC/ROTS, but still a lot).

What played in Abrams's favour a lot is the OT's familiar battered look - CGI was much easier to hide with that look than with the bold, sleek and pristine sophistication of the designs for the prequels - that and some over the top location design (like the Gungan city, for example).

In all fairness to Lucas, he too used a lot of practical elements in the prequels, especially for Tatooine where he used it all... tons of extras in suits, puppets, partial or full real sets for Anakin's home, for the Lars's, for the Tusken camp etc. He also built fully the interior of spaceships like Amidala's, and part of the exterior for some scenes. Obi-Wan's fighter too etc. Lucas also used many models for vehicles which were composited over real or partly/fully CG plates.

Even more than CGI it's the too sleek retro futuristic look of the prequels people didn't like - but they blamed it all on the VFX that were in fact (with a few exceptions) really top notch for the time. That's another thing: CGI has progressed massively since the prequels - it blends more seamlessly now, if the director is clever not to abuse of those effects, and most of all if he refrains from using CG to create scenes that are impressive yet so fully impossible physically to film that he breaks the audience's suspension of disbelief.

Abrams sure made better use of CGI than Lucas did, but he was also more clever in the way he sold it to the audience by making people believe, well ahead of the movie, that there wasn't a lot in there. In the days of TPM, the good folks of ILM were all over the place telling everyone in interviews how awesome and innovative the VFX were. With the backlash then (and over the recent years) the order of the day is to be more discreet, and emphasize how much is real instead...