I like TOS best when it offered strong morality tales. Yes, it often went over the top, but so many of the films never even bothered to try. (Anyone care to suss out a moral for NEM?) And so TVH and TUC, to me, are most like TOS.
Huh? Nemesis is probably the most blatant one out of all the films; What makes you who you are, nature or nurture? And then it tries to answer that question with "neither", that's it's our choices that define us.
Whether you like the film or not, it definitely had a moral.