We laud GR for trying to woo established SF writers to write for Star Trek
yet it's ironic that many of them had a challenging time to write for the show. They seemed to be stuck with the idea of writing for an anthology and had a hard time wrapping their heads around working in someone else's sandbox. And they could resent having their ideas rewritten to fit within the series format and what had already been established.
It could be they also dreamt big with a show like Star Trek
coming onto the scene and needed to be reminded of the constraints of television including budgetary concerns.