I think you're (unintentionally) framing this in a way that centres the adult-oriented books that you value more highly, to the exclusion of the ones that you don't hold in any esteem and that's a real trap that people can fall into.

Let me put it in different terms to illustrate the point.

Imagine if I told you that any adult TV show is more deep and meaningful than any children's/youth TV show. I'm sure that immediately you're thinking of the most trash-tier reality TV show and comparing it to a celebrated TV show which is aimed at a younger audience and you're thinking "Hang on a second... that's a flawed proposition" and you're right to think that. Not to mention there's a really good chance that you haven't even considered that infomercials are undeniably aimed at an adult audience nor considered the implications that this has for the argument.

So, why is it different with books?

There are some really shallow, vapid books aimed at an adult audience and there are books aimed at a younger audience which are deeper and more meaningful than a Harlequin romance novel or a Chuck Tingle novel for example (I'm making an assumption here - I've never read any Chuck Tingle before.)

Of course this is all subjective and it's a matter of taste, but isn't that kind of the point?

You could give The Yellow Wallpaper to a misogynist and they'd shrug their shoulders and be like "Women... amirite?" or you could give Things Fall Apart to a western chauvinist and they'd see little value in the book or you could give something like Infinite Jest or The Naked Lunch to a lot of people and they'd see no value or meaning in it.

Likewise, books aimed at a younger audience are likely to be more meaningful to a young audience than The Old Man and the Sea is to an adult. And vice versa.

But I'm not telling you off for having your own preference and for finding more meaning in the books you are drawn to. When it comes to how we make meaning and what value we place in art, this is something that is deeply personal and it's entirely subjective. There's no right or wrong and there's no objective better or worse in this experience, it's all simply a matter of preference and we should embrace this fact.

You don't have to share in someone else's love for YA fiction, for example, but there's no need to try and impose your preferences on them either.

With that being said if you're an adult and your frame of reference for politics is YA fiction, you're playing around in the shallow end because this is a matter of facts and not simply taste; if you use the Star Wars movies to inform your understanding of medicine then you should be prepared to have your opinions disregarded by medical professionals, and rightfully so. That doesn't mean you aren't allowed to have Star Wars as your favourite franchise. It just means that it has its place as art and that's where it belongs. The same can be said for fiction novels and politics (although I'm sure that someone's going to chime in with a good counterexample now that I've gone and made that my position.)