Wow was popular back then because mmos were fresh and new. Trends change like people listened to Led Zeppelin in the 70s and now mumble rap is popular.
WoW is still doing great compared to other mmos and it’s not realistic or likely it sees the same amount of players as it did back when it was the cool thing to do. And I really do think this is an important thing to talk about when someone says WoW used to be more popular.