Paramount decanonized TAS in 1979 because there was still a legal question as to whether they would owe royalty payments to Filmatilon for any elements 'borrowed' from TAS for the feature films or TNG. Since Filmation folded an d the rights for TAS all reverted to Paramount/CBS <--- That's when TAS was re-cononized.
As for the film GR considered non-canon - I thought it was STIII:TSFS because he didn't like that Kirk self-destructed the original U.S>S.Enterprise? (Which GR considered as a 'Star Trek' character; and NO MATTER the situation, it's something the 'real' James T. Kirk would never do.)
I WISH STV:TFF didn't exist, and I tend to ignore it myself; but hey, it is what it is.