Sounds like a problem of unrealistic expectations. I read
Animal Farm when I was a kid and enjoyed it. No-one told me that it was going to profoundly change my life, and it didn't. Neither did my chemistry class, or my math textbooks, or most of the other stuff I learned in school. There's value in reading significant works of literature, both inherently and because it increases your ability to engage with long and complex texts. Obviously, reading
Vanity Fair is not going to confer some kind of profound knowledge, or enable you to do anything in particular that you couldn't do before.
I think one thing that you do get out of engaging with assigned texts is the ability to decenter your own judgment just a little bit. Instead of reasoning "this novel is boring me to tears, therefore it sucks", you start to think "what is it about me that makes me unable to appreciate this classic novel?" That doesn't mean you have to like the novel, in the final analysis, but it's a useful thought process to go through.