The theme of the novel is loneliness, modern existential loneliness exacertabed by the horrors of the recent war and the looming threat of a nuclear World War III. Holden Caulfield is especially vulnerable because he obviously has a near-genius I.Q. This explains why he is able, at only sixteen, to write a full-length novel full of sensitive character descriptions and original observations about all sorts of things. (He is, of course, the creation of a much older man, J. D. Salinger; but Salinger manages to create a convincing illusion that we are actually reading the words of an intelligent, lonely, confused adlescent boy.)But his high I.Q. sets him off from other people. They can't understand what he is talking about. His encounter with the young prostitute is a good example of the distance between Holden and the average person.
Holden only vaguely understands that his own parents do not really want him. That is why they sent him off to boarding school. Those elitist private schools are full of unwanted children who are strangers in their own homes when they return on holidays.
Holden is his own worst enemy. He is looking for companionship, but he is so discriminating that he rejects nearly everyone he meets for one reason or another. He considers a lot of people "phony." This is undoubtedly true of a lot of people. They do not want the kind of intimacy that Holden is seeking. That kind of intimacy is rare in the world. Most people wear masks to interact with others. This is especially true among people who live in big cities--and New York is the biggest city in America. Holden is naive to think that he is going to get much sincere contact with a bunch of strangers during his short visit to a relatively strange city where everybody is struggling for survival in a Darwinian-Malthusian environment.