Let's set aside for a moment what TNG et al gives us evidence wise for the dates of the TOS movies, just for the sake of argument. What do the movies, and only the movies, tell us about the passage of time? TMP is at least 2.5 years after TOS, given Kirk's line about his time as Chief of Operations, and the Enterprise has been under refit for 18 months. TWOK gives us a date of 2283 for the bottle of Romulan Ale, and Kirk and Khan both place the events at least 15 years from the events of Space Seed. TVH tells us that the crew has spent 3 months on Vulcan. TFF takes place at least 3 weeks after TVH, from Kirk's comment about how much time he gave Scotty to put the Ent-A back together again. Finally, TUC has to be at least 3 years from TFF, because Sulu states that his first assignment as Excelsior captain has been that long. McCoy also states that he has been the CMO of Enterprise for 27 years. So where does that leave us in terms of the passage of time?
Just following those dialogue references (and ignoring anything from TNG on), we can place TMP at TOS +2.5 years at minimum, and TWOK at TOS +10.5 assuming the end of TOS is at least 2 years after Space Seed. Dating TSFS, TVH, and TFF is harder, but TUC is at least 3 years from TFF, and assuming McCoy joined our heroes at the very beginning of TOS that places TUC at TOS +24 years. This timeline varies considerably from the dates in the Encyclopedia, but it is reasonably consistent with what happens on screen. So what does that leave us in terms of this thread, and the careers of our heroes?
Our heroes have 2.5 years between TOS and TMP, a whopping 8 years between TMP and TWOK, and at least 3 years between TFF and TUC, and 24 years or so between the end of TOS and TUC. So, over 24 years of their careers post TOS, we see nothing of 13.5 years of that. If you look at the dates in the Chronology/Encyclopedia, the gap between TOS and TMP remains at 24 years, the gap between TMP and TWOk expands to a massive 12 years, and the gap between TFF and TUC grows to 6 years, leaving 20.5 to 21 years of these characters lives and careers unseen to us.
What are we shown of this time, this gap of 13.5 to 21 years? We see all of our heroes advance in rank, some of them several steps. We see in TWOK that Chekov has ascended to XO on another ship, and in TUC Sulu has ascended to a command of his own. I don't think any of these things point to our heroes having stagnant careers, and I don't think we can assume the presence of everyone on Enterprise in TWOK and TFF by itself as evidence that these people have spent the better part of two decades going nowhere and doing nothing.