There are (and always has been) many groups - it's particular memes or styles/groupings of memes which tend to be specific to some particular subculture, not the term "meme". Perhaps decades ago the internet was narrow enough to be considered a single in-group, but IMHO that wasn't the case already for the first memes that the OP (and their particular ingroup) considered, i.e. in the mid-2000s. It's obvious that the memes of the older in-groups are not known by OP and their in-group, and in a similar manner OP is complaining that they're seeing memes for which they're obviously not the in-group anymore; and because of the regionality of memes IMHO it never was a shibboleth for just a single group; both the concept and the name was used worldwide in disconnected cultures speaking in different languages with each other instead of the english-centric majority of internet.