What Abrams meant by this was that the Original Trilogy had a gritty "lived in" look to it that made everything look like a real place. Lucas' reasoning for this was that technology didn't really advance under the iron grip of the Empire so everyone just used what they still had and everything ended up looking lived-in. During the Prequel time period, it was a more refined time before the Empire. That means everything was kept up well and looked slick and very Flash Gordon-like. Abrams wants the Sequel Trilogy to reflect the lived in look of the Original Trilogy more. One can assume that even with the Empire gone, people won't bust out the floor buffers and paint to keep things up anymore.