You said it yourself, TWOK is about kirk's midlife crisis, with the narrative coming from khan's desire for revenge. Genesis is a smaller part of the plot, is is mainly there for kirk's son to argue with him, at the end of the film the genisis subplot isn't really resolved because that's not what the movie is about. I don't see how Kirk finding out he has a son while battling an enemy that he has fought before, is going where no one has gone before. TOS had its fare share of action stories. But it also had plenty of episodes with a slow moving plot, that had the drama come from the unknown (aliens, or being that the crew couldn't explain that they had to understand in order to overcome).