Well, as stated, Roddenberry didn't support a number of the movies or later TOS episodes by then.
Which begs the questions, in my mind, at what point did Gene Roddenberry become out-of-step with and a detriment to his own creation?
My personal answer:
Actually, the '70's. During the 1970's his convention appearances and college lectures represented a large chunk of his income, and I think he definitely tailored his speeches and answers to what he felt was "selling" - not necessarily what had been in or alluded to in the live-action series.
Pretty much, honestly, when he distanced himself from the series in 1968 until his passing in 1991. Much of the third season's uneveness was due to his odd level of participation. Then one finds out how a live action motion picture could have been possible in 1974 but was reportedly sunk by GR over relative "nickels." Recycling various Trek episodes in his script for TMP. His objecting to and bad-mouthing various "Star Trek" projects starting with "The Wrath of Kahn". And then all his strange edicts in TNG.