The God Thing said:
...in every script and treatment of every 1970s revival I have ever read the redesign and refitting of the Enterprise was a key plot element. GR would never have pulled the rug out from under us by claiming that the TMP Refit is what the NCC-1701 "always looked like".
TGT
Funny that he was willing to do so with the Klingons (and the fans never accepted it, resulting at long last in the weak as water ENT retcon--lucky us) and telling: Star Trek
was the Enterprise so far as Roddenberry was concerned, the Klingons merely a rarely seen adversary.
The 1979 update comes in a completely different context, anyway: we'd only ever seen one Federation starship design and it had grown familiar and dated by association. In order to make the jump in the next decade (or the decade after next), it made sense
then to make the design even more futuristic (and kudos to Jefferies and Probert for continuing the smooth-hulled roundedness of the original--accentuating it, even--rather than aping the Star Wars aesthetic), to re-invent it to make it new as well as familiar. Since then, we've had
as major classes of starship the Miranda, the Excelsior, the Ambassador, the Galaxy, the Intrepid, the Defiant, the Nebula, the Sovereign and the NX. In addition, we've had innumerable pipsqueak ship classes, like the Oberth, the Akira, the Norway, the Steamrunner. There is absolutely nothing they can do to the Constitution design that will make it seem fresh or stand out in that mob
save leaving it the fuck alone. This isn't fan-wank pandering, it's common sense: the original design has become a classic by virtue of the overcrowded field it has spawned--kinda like TOS itself, when you think of it: Once again, the Enterprise is Star Trek.