Excelsior only gradually become accepted. Part of this was because some didn't care for the Galaxy-class and this the Excelsior became better by comparison. Others started to like it after it became Sulu's ship, and thus started to become a hero ship in its own right. Also the shots of it in Star Trek VI made it seem better than what we saw in Star Trek III and the small model next to the big Galaxy model in TNG. The big powerful Excelsior next to the Enterprise-A made a better impression than it did as "the Great Experiment" that stalled, with a satisfying clunk, trying to enter transwarp after the Enterprise was stole from spacedock.