There are two main problems with CGI.
1: They age horribly. I was watching What You Leave Behind a few days ago and I noticed in the last scene when the camera was panning out from DS9 to outerspace that the station was obviously CGI. Watch Lord of the Rings.
2: They look to fake. Can't capture human emotion properly. The scene in First contact with Picards eye or in DS9 when the camera was focused on Ezris eye had more range of emotion in it then an entire episode of CG can.
In my opinion people are to crazy over CGI. It should be made to complement the scene not take over it like Star Wars. If you have it all over the scene or make the entire show out of CGI then it will come off as fake and in a few years it will look horrible,