I read it a long time ago and like you have very little recollection of it. However in high school we also read Homer and several plays by Shakespeare and remember a lot of details - I think my English teachers did a great job of explaining the context and chairing our discussions about those other works. I was thinking it’s hard to relate to Tom and Daisy in high school but then the other works are separated from us by culture and centuries (though to be fair translations we read for Homer are each a work in themselves)
Homer and Shakespear at least have the advantage of being referred to all the time elsewhere. If you don't at least know the basics of Romeo and Juliet you're going to be confused many times (there's something called Romeo and Juliet laws, for goodness sake).
I can't recall anything referencing the Great Gatsby, but maybe they went over my head because I can't recall anything about that except that the Gatsby was apparently Great.
OK, that's your experience. On the other hand, https://eu.usatoday.com/story/life/books/2013/05/07/why-the-... offers some pointers as to why a fair number of people have a more positive reaction. Although it is, in a way, an obvious statement, the very last line somehow always stuck with me reading it years ago "So we beat on, boats against the current, borne back ceaselessly into the past."
>Homer and Shakespear at least have the advantage of being referred to all the time elsewhere.
That's true for most of the works in the canon of works that are commonly taught in schools, people that didn't pay attention tend to miss them or be confused by them though. Every time we remove some work by Dickens or Shakespeare from our canon, we lose a bit of that shared culture.
I remember not liking the characters and wondering why should I read this, but now I have come to appreciate the value of understanding the view points of other people in spite of how I might feel about their actions and words or be distanced from their existence by virtue in this case of the wealth and privilege available to them.