One thing I've always liked about the classic Forbidden Planet is the dialogue. Other than some throwaway technobabble there's no attempt at "futuristic" speech, just characters speaking intelligently in complete sentences. Dr. Morbius, in particular, has the speech patterns of a highly educated and literate man who carefully chooses his words before they leave his lips. How many of today's actors could deliver those lines without sounding as if they're reading from a prepared speech?
Maybe it was meant to be a riff on the overuse of "man" by beatniks, hipsters and hippies as a conversation-filler.I remember Doctor Who comics published in the 1990s did a story set in the near future (which I think was supposed to be 2010 or so) made their attempt at creating future slang, which just came off as bizarre. IE, everyone referred to each other as "child" for no real apparent reason.