I think what happened with Trek in general is that during reruns it was watched by young kids (myself included) even though it did not target that demographic. That explains TAS. Kids are more sophisticated than most adults give them credit for, beyond a certain age at least. When I was growing up I resented the way things like Superfriends talked down to kids. That sort of thing persisted through the 80s with stuff like He-Man which featured "moral" segments at the end. There's a sweet-spot for family entertainment that I think companies like Pixar wound up striking in which you can engage kids with a fully fledged storyline that neither talks down to them nor bores their parents. Even though TMP got a G, I don't think it hit that sweet spot, not just because of the philosophical aspects of V'Ger, but also because the characters lost the casual familial quality that they had in TOS. Certainly something like Trek IV was a family film, and was the highest grossing TOS film, right?