I'm not convinced this is specific to the format (or the platform). Whenever I try to search for a specific meme or gif on google, I find huge numbers of basically identical copies that come from separate sources. I've seen complaints on humor subreddits about how people repeatedly post copies of the same jokes, often without attribution.

Out of curiosity, I asked my wife about this trend specifically, and while she was familiar with the joke, she has yet to see any instance of it on her page. I have to wonder if people who are experiencing stuff like this are mostly just getting stuck in a bubble and not pushing through to other content. There's an argument that learning how to interact with the app to make the algorithm work for you isn't a great experience, but there's a large volume of people who use and enjoy the app without complaining about this issue. I'm not particularly convinced that all of these people have gone numb to brainrot to the point that they enjoy seeing the same joke 20 times in a row compared to them just having a better experience from seeing a wider variety of content.