For me, it'd probably be the obsession with streaming K-pop stans have nowadays. Back in 2007 no one really cared how many YouTube views a song got (mostly because there were, like, no official channels uploading K-pop MVs then), but now streaming is basically essential. to being a K-pop stan. There are even some (very bad) groups of stans who'll guilt trip a fandom if their group's MV doesn't get as many views as they usually do. Very odd behavior if you ask me.
But what thing that happens nowadays in the K-pop world do you think would shock a 2007 stan if you told them about it?