With old-style effects there is a level of tangibility. The object is/was there. With computers, its far more difficult to have that same effect. Sure you can have a person stand-in, like in the case of Jar-Jar, but its not the same.
The effects of 3PO falling, then flying in that droid factory looked, to be honest, cheap. If they had actually dropped a 3PO suit, it would have looked better.
Its like the difference between a live-action movie, and a cartoon. CGI is just a really, really high-tech cartoon. EP1 is like Who Framed Roger Rabbit (allusion here, which had in it a Star Wars actor).