How bad was it around the time of TMP's premiere? Given how the film is perceived by the general public these days, I could imagine an almost palpable sense of "That's it???"
Imagine how dire it was for fans like me, attracted to the cinema by a huge-budget reunion show of a TV series I'd only really ever heard about, and seen a few cartoon episodes of? I stumbled across organised ST fandom a few weeks after being blown away by the movie, and immediately found about 200 kindred spirits, but most of them angry/disappointed/betrayed by ST:TMP - and some even telling me that I'll never be a "true Star Trek fan" because I wasn't there in the 60s.
I hve fanzines and letterzines here, from 1980, where people plotted angrily how they could shunt TMP (and its ugly Klingon "munchkins") into an alternate timeline where it could be forgotten. How dare Kirk leave his ship for the Admiralty? How dare Spock try to purge his human half? How dare McCoy leave kirk's side for all those years? How dare the SPFX guys change the Enterprise and the transporter effect? Those uniforms! Where were the Tellarites? And so on!
There were two camps re Gene Roddenberry though: "Fire him and let someone else do another film!" and "I refuse to see a sequel unless GR is exec producer". Controversy and polarized opinions over a ST movie are certainly nothing new.
However, there were
plenty fans who embraced TMP - and their frequent returns to the big screen no doubt helped to improve the box office take. Even many of the detractors saw the movie lots of times.
TMP and JJ's film are still my favourite movies of all time.