I think you're confusing plausibility and believability with "real,", "factual", and "educational". Your story still needs a degree of believability for readers to buy into it. Even if you have wizards slinging magical spells at each other.

Not at all

I think you're getting hung up on the word "symbolism" tbh. And taking it to mean that the author intended this thing to be representative of this thing. When like some people said, really, your specific example of the Holden on the hill is about establishing tone, mood, and characterising Holden.

It's not so much about it symbolising that he's isolated from his peers so much as establishing that he is.

Anyways, the best thing my lit teacher ever told me is that there are no right or wrong answers. Just use the text to bring evidence to support your interpretation.

At the end of the day your argument has to have supporting evidence from the text and it has to make sense.

I have one friend and they're someone I know IRL. I don't use the social aspects of Goodreads. It's really just a digital bookshelf for me to keep track of the books I have read, where I'm at in the books I'm currently reading, and the books I'm interested in reading.

ETA: I don't even read the reviews on Goodreads, or look at the star ratings for that matter.