What I don't understand is why nobody seems to notice that TMP stole just as much from TAS One of Our Planets is Missing as it did TOS Changeling. A large space cloud threatens to destroy a Federation planet. The Enterprise flies to the center of the cloud where Spock mind melds with the intelligence behind the cloud.
Actually, readers' letters in "Starlog" (and "The Best of Trek"?) in 1980 certainly did discuss how TMP seemingly lifted story material from TAS's "One of Our Planets is Missing".
Marc Daniels already had a TOS script sitting in the slush pile when the series ended, and it may have made it into a Season Four (along with Alan Dean Foster's double-length Klingon episode, which was mined for "Star Trek Log Seven"). Daniels' one-hour script was called "The Beast", and I'll bet it was retooled as the TAS episode.
Not to mention the giant planetoid in orbit of Vulcan (not a moon because Uhura was told in TOS that "Vulcan has no moon"). And the second turbolift on the bridge! And the location of Klingon ships' torpedo tubes!