Holden is the one telling the story, so his tone is Catcher’s tone. We don't think we need to spin you a large defense for our use of adjectives such as "cynical" and "judgmental"—just pick a page. But how can the tone be both cynical and compassionate? Check out Holden's interaction with Sunny-the-prostitute:
I took her dress over to the closet and hung it up for her. It was funny. It made me feel sort of sad when I hung it up. I thought of her going in a store and buying it, and nobody in the store knowing she was a prostitute and all. The salesman probably just thought she was a regular girl when she bought it. It made me feel sad as hell—I don't know why exactly. (13.52)
We know why: he has compassion. He’s cynical—he sees right through Sunny’s pretense of being a seasoned whore, and he makes sarcastic digs about how she’s a bad conversationalist—but he’s compassionate. He sees her as a real person.
At the same time, Holden finds nearly everything to be depressing. Specifically (deep breath):
leaving a place without a proper good-bye, leaving a place with a proper good-bye, men in bathrobes, Vicks nose drops, Old Spencer's warnings, people who say "good luck," empty corridors in the dorm, getting ice skates as a present, getting presents in general, girls that travel to New York from Seattle to wear ugly hats and see the first show at Radio City Music Hall, hotel lobbies, people laughing on New York City streets late at night, prostitute's dresses, having money, not having money, inexpensive suitcases, money in general, nuns and their lack of swanky lunches, girls and their potential futures, being drunk, being told he doesn't like anything, sleeping in train stations (although, to be fair, this is objectively depressing), the fact that Mr. Antolini made a pass at him, the fact that Mr. Antolini might have not actually made a pass at him after all, vulgar wall graffiti, the fact that he couldn't take revenge on the person who wrote said graffiti even if given the opportunity, Phoebe or people like her saying the word "please," and … the fact that he has told us any of this at all.
And then there are the digressions. Check out his discussion with Mr. Antolini (before the big education lecture) about the Oral Expression class at Pencey. Holden failed the class because he felt digressions were important. He makes a few key statements:
And notice that what Holden’s doing is … telling us his story. Out loud (supposedly). You might even say that it’s a type of Oral Expression. He's not writing it down and handing it over as an essay; he's telling it to us. And that means, everything he just said to Mr. Antolini, he's actually saying to us. He's not devoting three pages to a random discussion on oral style for nothing; he's defending his narrative technique.
Why is Holden telling us about Allie's baseball mitt? About the time he played checkers with Jane? About James Castle jumping out the window? Because (1) it's more interesting, (2) he didn't know that was what he needed to talk about until he started, and (3) he couldn't simplify and unify these events just because that would make it easier for us. That’s on us.