[cld8483]

You may be right, but I'm not convinced. I believe many Jules Verne novels were once considered "young adult" fare, but (in the original unabridged forms) became challenging for young adult readers in the 20th century. I think natural drifts in language are a major factor in this. The stories and characters are generally simple, but the texts themselves become more challenging as time passes.

Or take Shakespeare for example; he wrote for the unwashed masses yet his writings are considered sophisticated and challenging today. I have an anthology of English renaissance drama from various playwrights that I revisit from time to time. The stories are usually quite crude and funny (example: https://en.wikipedia.org/wiki/%27Tis_Pity_She%27s_a_Whore), but understanding them well enough to appreciate that humor can be a chore. I don't think these stories were considered difficult originally, but became so over time.