Perhaps "dumb" in the sense of "that looks like a dumb way to spend all your free time and money".

I guess that the appeal of Pokemon and similar dumb phenomena (somebody correct me if I'm wrong, I'm too old to have played any of these games myself and too young to have children who have) is twofold -- there's the "game" part and then there's the "collection" part. The "game" part is pretty "smart" as a game, and one could easily imagine a card game with a similar sort of game mechanic that could be bought for a few dollars. But it's the "collection" part of the game that makes it so addictive, expensive, insidious, and the source of much needless (and dumb) social anxiety among children.