Practical sets, extras, and props, including practical mechanized droids rolling past, provided an aura of reality that CGI just flat out hasn't been able to match. This is one reason why I prefer the original cut of the 1977 film to the special edition. It just better feels like you're really there. Call it an ineffable je ne sais quoi, if you like.
Yeah, the whole feel is different. One of the things that was so cool in 1977 -- even if you weren't conscious of it -- was the way Lucas used the documentary style framing, like everything you're seeing is normal. There are monsters and vehicles and robots all over the place that barely get in the frame, or move through without any attention paid to them. SF movies hadn't been like that before, they generally put the fantastical and spectacular stuff front and center for everyone to marvel at. After the CG stuff was put in SW, the emphasis in those shots, too, seemed to shift toward emphasizing the effects.
The old Mos Eisely felt more like a near-ghost town in a Spaghetti Western: Not much going on in the street (too hot) but full of menace anyway. The new one seems more like a travelogue. And that's aside from the absolutely awful editorial decision to undercut Ben's serious word of warning by following it with a pitiful Jawa sight gag.