If anything, he's too empathetic. I think readers often confuse his tone with his worldview and his observations about people. His ironic and often sarcastic tone masks his sensitivity to the people around him. It's a defense mechanism. Only a sensitive soul could see some of the things he does. When Holden cuts off his thoughts it's not Salinger suggesting something about Holden's "limited cognition"; it's Holden feeling vulnerable. Holden is quite perceptive, but his ability to perceive stretches beyond his ability to reconcile the way things are with the way he wants them to be. Additionally, it's important to remember that the point of view of the novel is in-between first person and stream of consciousness, so it requires a more nuanced reading. Readers need to keep in mind that Holden is young and grieving over his brother's death. All too often this book gets read in high school as a Bildungsroman, which I argue it is not (it's actually closer to a Trauma narrative). The coming of age lens that some teachers apply to it comes from a superficial reading and actually causes young readers to miss the parts of the novel that make it a great work.