http://uproxx.com/movies/star-trek-gene-roddenberry-falling-out/

1979’s Star Trek: The Motion Picture is many things to many people — the first time these beloved characters ever appeared on the big screen, the beginning of the Star Trek movie universe, and the anti-Star Wars. However, it also marks the last significant contribution to the Star Trek movies by Gene Roddenberry, the man who first brought the idea of Star Trek to life in 1966. That’s because Paramount removed him from his supervisory role after the film’s box office numbers came back.

“Wait a minute,” you’re probably thinking. “Why would Paramount ditch the guy who created the property in the first place?” Money, for one thing, was definitely a major factor in the studio’s decision to oust the man much-beloved by science fiction fans at the time. Yet to truly understand the division between Roddenberry and studio executives, we have to dig a little deeper into the complex muck that was and will always be attached to Star Trek.

By the time of TMP (and especially TNG) , Roddenberry seemed to be surrounded by yes men who didn't stand up to him. TMP was a long, talky, existential space journey a la 2001: a Space Odyssey. Not a horrible movie; just not one that evokes the campy fun of the original Star Trek series.

If you want to see what Roddenberry REALLY wanted to do with Star Trek from the very beginning, then you need to watch the pilot episode "The Cage." NBC rejected it because they wanted something more action/adventure-oriented, and so instead we got the series with Kirk and co., which was arguably a watered-down version of the original concept.

Imagine if the whole series had developed along the lines of "The Cage"; more cerebral and intellectual science fiction, fewer fistfights and space battles, and less cheese. That is what Star Trek was really supposed to be. And so Star Trek: The Motion Picture was the perfect follow-up to that concept.