That's not why GEN sucked. The E-D was destroyed, and substituting Earth for V3 would just mean there would be a lot more ships present to destroy the BoP, do something to neutralize the threat of the Nexus and make it even more ridiculous that the E-D could be destroyed.
Veridian III definitely was a better location. Not just because Trek means going "out there".
Every time Earth was used as a plot point in the TNG movies, it had at least that one reason to suck:
Generations: They already did the thrill of being in Earth's solar system at the start, where no other ship was properly available, and everybody knew who the El Aurians were, somehow. How those ships got to the Sol solar system by the seashore there after the Borg assimilated their homeworld also begged too many questions... plus, Guinan would have been better off with electric candles...
First Contact: Something about the Borg going into Earth's past to assimilate the future despite arriving in the present
before going back in time just for the cheap thrill of killing off drones needlessly... then again, if they had won then the Enterprise's future wouldn't have transpired so those drones would never have died... unless they came from the 1701-D, in which case it starts to get a little more complex...
Insurrection: No Earth in sight, but it didn't stop the movie from sucking anyhow.
Nemesis: Ostensibly insane, instead of using Earth as a generic crowd-pleasing plot device as locus of action for the climax, Shinzon's whiplash plot motivation change from going after his Romulan captors to destroy Earth because somehow Picard is responsible for everything the Romulans did, including creating him in the first place... wasn't really believable or compelling.
Trek IV did Earth the best, but it was still tangential and by then everyone cared about Kirk's homeworld, even if it wasn't ours.