I'm not sure all of those leaps are true, might be a bit of fundamental attribution error in your assessment.

Yes, yes! I read it as an adult after seeing the book widely criticized on Reddit. I was blown away by how sympathetic I found a struggling teenage boy. What it says about a reader if they can't empathize with Holden is indeed the saddest part - I am disheartened at any lack of empathy for Holden given his circumstances.

I do wonder if many people's perceptions are affected because they were forced to read it in school as a teenager. I imagine under those conditions and at that stage of life it would be harder to understand Holden.