There isn't a sixteen-year-old alive who understands that; there isn't a forty-six year old who doesn't.
And yet this is exactly the kind of classic material which is forced on teenagers in school. They don't comprehend it, they don't enjoy it, and the very best you can hope for is that in 20 years later they won't be too stubborn to read it again.
Some people never DO consider reading those books again. They tend to be non-readers in any case, which includes far too much of our adult population.
There would be many fewer non-readers if early reading experiences were made fun. The classics aren't.
I could not disagree with you more, however. Teenagers as a group sink to the lowest common denominator. They have to be pushed a bit, or all they'll read is trash if they read at all. In my day it was the Hardy Boys and Nancy Drew, now it's the Goosebumps (although that's really preteen) and those awful Gossip Girl books.
Once you get them into the good stuff, they seem to like it. Mark Twain is (I think) the best American writer, and he's perfectly accessible to kids even younger than high school age. Much will go over their heads, but much is retained and they can come back to re-read Huck Finn when they understand the gravity of that, "Well, then, I'll go to Hell!"
BTW, I was in the best prep school in Atlanta 30 years ago, and Moby Dick was NOT taught. It isn't taught in that school today (my daughter just graduated there.) I took an entire course on Melville in college, and that's about the first time anybody can begin to appreciate him . . . of course you can't appreciate The Whale fully until you're well into middle age.