The comment you're responding to is talking about books that students will "barely understand". You're talking about subjects teens aren't interested in. The comment above says nothing about interest and specifically does not advocate against teaching things to teens just because they aren't interested in them; only if they won't understand them.
Even if you don't fully understand it the first time around, these are cultural reference points, so at least when you hear someone reference them, you'll have an idea what they are talking about and can get the point of what the adults are talking about. Then later if you ever read it again, you also have a better understanding of its place and get a better second pass understanding.
There is also the role of simply communicating to the next generation that society values these books, and they are important for some reason. Even if you only get one shallow layer of meaning at the time. Same with history and everything else. It's a time to get a first taste of what these things feel like.
>The comment you're responding to is talking about books that students will "barely understand".
That's how you get to understand something you "barely understand". You dive into it, and gradually you understand it better.
I understood classic novels in high school just fine. Further experience reveals more layers, but you still get lots of life lessons, and poetic moments, and better grasp of people and life, and introduction into a culture that's not just consuming slop, from reading them as a teenager.