There is of course more to it than that. In order to keep World of Warcraft's system requirements low from the start, the designers purposely created a simple yet beautiful style. It also really set the game apart from other MMOs at the time. It is a bit cartoony, though, as critics have said over time.
I used to play EverQuest during its cartoony days. I know my gnome looked like every other gnome, but she was my gnome and I loved her. Then The Shadows of Luclin landed and brought with it increased system requirements and a non-cartoony graphics "upgrade." Bye-bye, adorable gnome -- and bye-bye EQ for me.
Personally, I want WoW to keep its iconic look, but I agree with just about everyone else that it's time for an overall upgrade. Don't give me an attempt to look realistic. I want the developers to say, "Here is your beloved character, now with more polygons!" The pandaren still fall in line with WoW's original art style -- but the animations, the details! So wonderful.
Do you like the art style of World of Warcraft, or do you think that it should be less cartoony? Let's assume we all agree that the older races need graphics upgrades. Do you think they should drastically change? Do you want to keep the same look, just prettier? Or do you want a full overhaul with a more realistic slant?