World of Warcraft is well over a decade old now. That is pretty crazy, especially considering that the game is still susisting on a subscription service which is a paymodel that is certainly on the wain.
The game still has a massive pull though, as evidenced by latest expansion Legion's sales numbers. It's been announced that the expansion sold a staggering 3.3 million copies on day one. This matches the record of Cataclysm, which is pretty crazy to think after all these years. It also sports the most ammount of players on at the same time for a launch week since Cataclysm.
The enduring popularity of World of Warcraft is mindboggling, but at the same time, it's not too hard to understand why. Having played Legion for a little under 10 hours now, I've really enjoyed it and quality on this scale often translate to numbers. If Blizzard keep making content that is great, people will keep coming back.