"John and Mary" is supposed to be a contemporary movie, I guess, and yet it's curiously out of touch. John and Mary shadow box uneasily with the American language, trying to sound like all people their age without sounding too much like any particular person. And this doesn't work. We don't feel these are two individual human beings; their vocabulary seems to have been chosen in a Gallup Poll.
Here's what I mean. The movie is about a boy and a girl who are maybe in their early or mid-twenties. One of the things all people do (even people in their twenties) is to talk about real things. Real names. Real people. Remember the argument about Norman Mailer in "Medium Cool"?
In "John and Mary," however, nobody says anything very characteristic. An example. The story opens in a singles bar, one of those saloons where everybody guzzles beer and tries to pick everybody else up.
The idea is to show Mia Farrow in some sort of interesting conversation that Dustin Hoffman can interrupt. That's how they meet, see! So Dustin eavesdrops while a collegiate type says: "A ten-mile traffic jam and people eating each other -- that's ridiculous it you ask me."