Gatsby is not about being a metaphor for anything in particular; it's a snapshot of a particular time and place, an account of
what a certain society was like. It's just an intriguing (and quite beautiful) story that captures the spirit of a certain era.
By analogy, what you wrote is like saying:
> The Mona Lisa? Roughly 75% of it is just kind of blurry. I can see her face in the middle, which I guess captures her likeness, but a photograph would've probably been better.
It's easy to miss the point or merit of these books in class: often they're forced reading, you read them too early, etc. I would strongly encourage you to pick up 1984 or The Great Gatsby again, and read it one of these days. You'll probably get much more out of it.
These books are considered among the greatest ever for good reason, and I'm sure you'll pick up on that if you give them another try. I think that Gatsby is so good that I re-read it once a year.