In my opinion (and everyone is entitled to one so here is mine) - the language of Salinger is dated and doesn't ring true with most teens these days. I think the themes are great - maybe timeless. Also, it works for a certain age and then it doesn't. FWIW, I went to a Catholic high school where it was banned.
You could say the same of Shakespeare. I think it's a great book, probably the best of the 20th century lit required readings I had. It was required reading (by me) for my kids. Yes, there is a certain age where it hits them harder, but I don't think it ever loses its relevance. Another in this category would be Lord of The Flies.
And now back to your regularly scheduled programming...
Both of the books you reference, "Catcher" and "Lord" are very much love 'em or hate "em type reads. No sense stating where I fall on either...nobody cares.
IMO, kids in the 60's/70's related more easily with Holden...I don't think kids these days would relate as much (as was mentioned above, due to language, slang). It's not required reading in our HS any longer, though "Lord of the Flies" still is. Very sad that Kurt Vonnegut is not required in our HS; his books are game-changers; even if you're not a sci-fi person (which I am not).