"IIRC, they were deliberately aiming for a "G" because they knew that "Star Trek" had appeal with families. "
There's no way TMP was going to appeal
to young kids. I was 9 when it came out and the cerebral plot was pushing it for me. The studio really made a mistake when they greenlit the script if that's what their intention was. Not only that, but the whole Deltan thing would have been pushing things for TV had they followed through with Phase II. TV standards and practice didn't start changing until the mid 80s, spearheaded by stuff like Married with Children.