In what way is World of Warcraft a "walled garden"? It's a single game. If anything, it's one of the most extensible online games made by a major studio. Do you just mean "walled garden" as "not FOSS"?

It's a game as a service, sure, but that doesn't make it a scam. That's like saying that renting an apartment is a scam because you don't own it. You can question if it's a good financial decision, but that doesn't make it not a fair exchange of money for a product.