This is a very confused article, I think. The fact that people associate these extravagant roaring 20s parties with the character of Gatsby has everything to do with his character and over-the-top parties being the strongest cultural touchstone that people today have with that era, given that almost all of us (in the US at least) have to read it in high school. The fact that the aesthetic qualities of Gatsby that are…
Consider Patrick Bateman. There are at least six things going on with Bateman memes: aesthetic appreciation for the movie and/or character, comedic irony, intentional contrarianism to annoy the sort of people who write articles about how much they hate Patrick Bateman, an obscure in joke, following the format without understanding the underlying work, and genuine unironic belief that he's a good guy.
If you are not familiar with the type of people who make memes about Patrick Bateman or name sandwiches after the Great Gatsby, you might misread them as misreading the work.