I don't think either Harve Bennett nor Nick Meyer were complete without the other, at least not initially. Bennett had more respect for the history, but he couldn't bring to ST the literacy of Meyer. Bennett had the story for STII, but he didn't have a working script. On the other hand, Bennett was more restrained and knew how to end the movie (whether they were actually going to bring Spock back or not).
Bennet was able to write III, and he understood that in order to bring Spock back it had to almost not be worth it (dramatically speaking). Still, the movie cheats in a way, and I'm right with Meyer when he said "Having seen it, I still don't believe it. But whatever, Spock is back." IV couldn't have worked without Meyer, but again Bennett was right (against Meyer's protests), in that they needed an extended epilogue to wrap up the subplots from III.
For VI, I think Meyer's movie (not Bennett's prequel) was the right movie to make at that time... especially after V had permanently weakened the TOS movie franchise. I don't find VI any more heavy-handed than Trek, by tradition, already was.
For a long-running franchise like this, you gotta have balls as well as brains and heart. If you don't have the balls (properly restrained) to assert your creative license, your franchise is already stagnant.