People like me, who were raised in a world overflowing with "classics", where the entire English curriculum was devoted to "classics", have no basis for comparison. They aren't "classics" to me so much as they are books, and respecting them simply because they're old is quite difficult when so many are so painful to read. I can't see these books in relation to their time, nor do I usually view them against modern literature, in part because I don't read all that much of it.
Furthermore, themes which may have been profound when a book was first published are by now part of the general cultural background, and so the notion that they're worth spending time on is a bit of a challenge. This is especially true of ideas which I reject but everyone accepts.
Here's Scott Alexander on a similar topic:
In a recent essay, Against Bravery Debates, I think I underestimated an important reason why some debates have to be bravery debates.
Suppose there are two sides to an issue. Be more or less selfish. Post more or less offensive atheist memes. Be more or less willing to blame and criticize yourself.
There are some people who need to hear both sides of the issue. Some people really need to hear the advice “It’s okay to be selfish sometimes!” Other people really need to hear the advice “You are being way too selfish and it’s not okay.”
It’s really hard to target advice at exactly the people who need it. You can’t go around giving everyone surveys to see how selfish they are, and give half of them Atlas Shrugged and half of them the collected works of Peter Singer. You can’t even write really complicated books on how to tell whether you need more or less selfishness in your life – they’re not going to be as buyable, as readable, or as memorable as Atlas Shrugged. To a first approximation, all you can do is saturate society with pro-selfishness or anti-selfishness messages, and realize you’ll be hurting a select few people while helping the majority.For the most part, I find a lot of the themes in older literature to be obvious and universal to the point that criticizing them seems like a duty. But perhaps that wasn't the case at the time. Maybe when these books were written such messages were actually useful. But how would I know, without actually taking a representative survey of what was being written at the time. Not the best works--the works that were so dull or bad that they were forgotten with a year.
Alternatively, it would be helpful to show how schools of literary thought react to one another. A certain mode of thought is in vogue, and then people get fed up with it and try something else, until people get fed up with that and try yet another thing. Sometimes this can be collapsed onto a simple one-dimensional axis, but usually the space is much larger than that.
In my English education there was a touch of this, but for the most part we glossed over the differences and relationships between different schools. I can't really blame my teachers for this--they were working within quite limited restraints--but the broader book culture would be well-advised to take this into account when demanding genuflection to the "classics".