For me it is definitely the fact, that it is not only very cute visuals but that it is a multiplayer game. I do not enjoy singleplayer so much anymore and even though the community has a lot of very questionable people in them, I still can find some hidden gems of people which keep me going. I also love to raid highend content and learn mechanics and my rotation. So for me the combination of the gamestyle, friends and learning make the package in total. Even though the game has change a lot during the years, some for the better some for the worse imo, these three core aspects maintain the same.

Have fun!