> So you end up doing a bunch of weird commentary on say a book where you as a teenager have no idea where to place it. Like if you read Dickens, will you know enough about the industrial revolution, the condition of cities at the time, and such? Will you know what kind of thing the characters would care about?

Well, you probably had some history classes, maybe watched a movie or two, heard something, maybe asked your parents or the teacher, etc. Also the books usually do set the scene by describing the environments, so you can infer from them.

It also works the other way, after reading that book it gives you some foundation for when you consume other media related to that period/place.