The ending dialogue between Kirk and Sulu sounds too unnatural/forced. As much as they wanted a Sulu spin-off, I don't think the fans at the time were ready for a Star Trek without Captain Kirk.
Marathon-watch a season of Star Trek: Chekov is trying to emulate Kirk but is too young and inexperienced to pull it off. The chicks swoon for Kirk instead, and Chekov usually guesses the wrong answer to a problem. (He falls into traps, which serves to warn Kirk / Spock so they can get it right.)or I am sure some fans would have loved to see Chekov
Undiscovered Country was transparently an effort to place IRL current events in the Trek universe. There might be a background universe where current events fit into the fiction nicely. Trek is not it; there is too much that had to have happened 1965-1980 but did not, to get from here to there. ("To Reign in Hell" describes Khan's childhood on Earth and does a good job with it. "Undiscovered Country" is a sloppy second-rate attempt to imitate what "Reign in Hell" achieved.)

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.