1. how many people don’t “hang out” in social media culture, and only circulate on there with family and peers using everyday idioms and emoji/abbreviation; if they use social media at all,
2. how many different, disjoint online cultures there are. Many things widely circulated on reddit and adjacent communities may never surface on some FB mom’s group
People maintain much more different lives from each other than you seem to assume, even among those that who are “terminally online” or that “hang out on social media”
I'm sure there are plenty of people who have used the "press F" meme without knowing the original context too.
You just had to have played that game, and the game isn't obscure. Call of Duty is one of the largest franchises on earth and I would consider it akin to something like a Marvel movie in popularity. If someone referenced a meme from a marvel movie, I wouldn't describe it as obscure.