I read Star Trek Movie Memories again recently (a great book, highly recommended), and I believe one key reason the TOS movies were better than the TNG movies is good old fashioned CREATIVE TENSION. The book very candidly describes how it was a power struggle to make every single one of the 6 TOS movies. At various times, Roddenberry, Bennett, Meyer, Nimoy, Shatner and Paramount were all fighting amongst themselves. And fighting hard. They had knockdown drag outs, they cried, they cursed each other, they threatened to quit … and it was all because each one cared so much about the material and wanted to improve it. The end results of these clashes were usually better films.
By the time Berman and the TV guys took over, they were a cohesive, formulaic unit and, aside from a few memos from Patrick Stewart or Brent Spiner trying to get larger and better roles, I’m sure people rarely spoke up and said, ‘This is bullsh*t, we need to do something else, or I walk!’ It was like Lucas and his total control over the prequels – not enough people disagreeing!