I guess what it all comes down to -- and this is solely personal opinion -- is whether you think TFF began with a good story that then got lost through bad filmmaking, or whether it was a bad story to begin with that was just made worse by the bad filmmaking.
I personally think TFF was flawed right from its inception.
Really, there wasn't even a need for this movie in the first place. TVH was a fantastic place for the TOS films to end, and TNG was at the height of its popularity. But instead Shatner decided he wanted to make a Trek movie, and Paramount decided to let him do it. And that's where the problem started.
1. Nimbus III - Why oh why on Earth was this shithole of a planet chosen for such an important meeting place for galactic dignitaries? You mean to tell me there was no other planet in the Neutral Zone better than this place?
2. The ENTIRE camping scene made me
painfully aware of how old these people are and that they really shouldn't be making movies anymore.
3. Spock's half-brother, and Kirk, McCoy, et. al not knowing about his existence - this has been commented on
ad infinitum, so there's really nothing new I can say about it, other than, "who the hell is Lawrence Luckinbill, and how did he get this role?"
4. The
only concept that I found intriguing was the "I can heal your pain" thing Sybok was doing. But the fact that a) Sybok was the one doing it, and b) that it made completely loyal friends and officers turn against Kirk without any real forcible influence just smacked of ridiculousness.
5. The Enterprise "being the only ship in the quadrant" thing has been done in other movies and shows before, but here it's just nonsensical. Really, a malfunctioning ship that seems to be the result of a severe design flaw is the only vessel Starfleet can send? What the hell was the Excelsior doing that they couldn't send it? And what about all those ships Starfleet has on Neutral Zone border patrol all the fucking time? Wouldn't they be, like, closer to Nimbus III than the Enterprise, which was in orbit around Earth?
6. A planet at the center of the galaxy, and the Enterprise can reach said center in less than an hour? Need I say more?
7. The Klingons were incredibly boring and dull, even more boring and dull than usual. Why were they even in the movie again? Oh yeah, so that Spock could use their ship's gun to kill God.
8. And finally, God, and why he needed a starship. And why Sybok was so incredibly stupid as to believe in this nuttiness. I suppose what Grant said, (i.e. the quest to find God who turns out not to be who you thought) could be an intriguing concept if it was done correctly. But that would work in more of an abstract way...not a literal way as presented here.
None of these points have anything to do with the movie's sub-par VFX, or the silly dialog, or the lack of action. These fundamental flaws simply cannot be fixed by editing.