I have to agree with the idea of the moon being a metaphor for sexual fulfilment although i think there is also an important reason why Cohen refers to the moon as the one "we" are after.
I think he means to correct the listener's false understanding and expectation of such romantic scene. "we" have very banally and obvious expectations from a sexual scene as this one, just as the woman in the song has, and Cohen is trying to mess up our romantic and tacky dreams telling us they will never fulfil our desires. from here: "lets sing another song boys, this one has grown old and bitter"
I have to agree with the idea of the moon being a metaphor for sexual fulfilment although i think there is also an important reason why Cohen refers to the moon as the one "we" are after. I think he means to correct the listener's false understanding and expectation of such romantic scene. "we" have very banally and obvious expectations from a sexual scene as this one, just as the woman in the song has, and Cohen is trying to mess up our romantic and tacky dreams telling us they will never fulfil our desires. from here: "lets sing another song boys, this one has grown old and bitter"