As it would for a 1920s fellow or gal to understand a 2020s meme ...
... or, since they didn't learn our pop culture in history class as we did theirs, maybe a mix of 1920s and 2020 memes?
That's the ticket. Let's use those as examples for what is a pretty dry acamemic (academeme?) analysis of some structural pillars of memery. First up is perhaps the most common part of the meme framework: the macro-image. Like How You Think You Look, a vast majority of all internet memes are a combination of an image or images superimposed with text that adds new context. Like the vibrantly colored "/s" that is Condescending Wonka. Or the already classic Distracted Boyfriend.
The image itself may often come with a subtitle, often a quote or catchphrase. But this text remains differentiated from the macro-text by virtue of no-one bothering to sync the fonts.
Also, while these images are typically static, more and more make use of GIFs. Or, as they would've called them in the 1920s, flipbooks.
Another very popular parameter also present in the 1921 meme is the use of multiple panels. Side-by-side images juxtaposed by the meta-text have been a key element of many popular memes from Tuxedo Winnie The Pooh to Drakeposting to modern examples like This Is Fine or Woman Yelling At Cat.
This brings us to semantics. All internet memes have to be relatable on a cultural or personal level. However, the most viral-prone find a way to easily combine the cultural references with personal insights -- by which I mean "Seinfeld asking the deal about airplane food" degrees of insights into the shared human condition. In the case of How You Think You Look, it draws people in with a pop-culture-combo of a Great Gatsby-esque playboy (the Instagram Influencer of the Roaring Twenties) and mention of the new technological fad of amateur flash photography. With the reader's attention grabbed, the meme then embeds into their brains with the common ground observation that we can never find a photo of ourselves that we truly like -- thus ensuring maximum virality.