I actually started re-reading Crime and Punishment right after writing my previous comment, because I barely remember anything after many years. These are the second and the third paragraphs, and reading this text now, in my forties, I perfectly understand everything that's written, and the emotions the protagonist feels, because I know by my very own experience what it is to pay rent, to be in debt, and to have no money. But as a teenager? No freaking idea.

  He had successfully avoided meeting his landlady on the staircase.
  His garret was under the roof of a high, five-storied house and
  was more like a cupboard than a room. The landlady who provided
  him with garret, dinners, and attendance, lived on the floor below,
  and every time he went out he was obliged to pass her kitchen,
  the door of which invariably stood open. And each time he passed,
  the young man had a sick, frightened feeling, which made him scowl
  and feel ashamed. He was hopelessly in debt to his landlady, and
  was afraid of meeting her.
  
  This was not because he was cowardly and abject, quite the contrary;
  but for some time past he had been in an overstrained irritable
  condition, verging on hypochondria. He had become so completely
  absorbed in himself, and isolated from his fellows that he dreaded
  meeting, not only his landlady, but anyone at all. He was crushed
  by poverty, but the anxieties of his position had of late ceased
  to weigh upon him. He had given up attending to matters of practical
  importance; he had lost all desire to do so. Nothing that any landlady
  could do had a real terror for him. But to be stopped on the stairs,
  to be forced to listen to her trivial, irrelevant gossip, to pestering
  demands for payment, threats and complaints, and to rack his brains
  for excuses, to prevaricate, to lie—no, rather than that, he would
  creep down the stairs like a cat and slip out unseen.

If we're going with a math analogy, I guess it's a bit like teaching them integrals in 3rd grade. You can do it, they probably have the raw IQ for it. But they won't really understand and appreciate it at a deep level (this is even a problem for people when they encounter integrals at the end of high school / early uni).

Novels like these need some life experience to really shine. A 13 year old isn't going to go "how does this writer see so clearly through so many of life's finer details", because they have never experienced 90% of what's being talked about.

There's a huge difference between purely intellectual subjects, like organic chemistry and integrals, and the mix of emotional and intellectual depth of a novel. A lot of the meaning of literary works is built on top of shared human experiences, just like the meaning of integrals is built on top of more foundational math. However, we don't have any good way (and certainly make no effort in school) to teach this shared human experience to pre-teens and teens.

A good part of the value of some of these works basically comes from recalling similar feelings you felt in situations similar to the characters, maybe comparing your actions at such times to theirs, or the reactions of other people you knew, etc. It's simply not possible to experience this part of the work as a teen. Perhaps one of the clearest examples of this limitation is in Lolita - the nature of the relationship described, the power and life experience differential, the contrast with the reader's normal interactions with children - are impossible to be conveyed to or truly empathized with by teens.

STEM subjects are actually taught in order with foundations first, etc etc. Literature requires understanding all kinds of context that they don't teach.

> Are kids "ready" to deal with organic chemistry? Or integrals?

Yes, absolutely. A kid can learn both of those things and understand them, assuming they have the proper foundational knowledge, taught to them in prior classes/years.

Most kids do not have the lived experience or emotional development to understand the complex adult themes written about in novels such as the ones being discussed. There's really no way to fix that aside from waiting until they're older.