It's not the power of the console, but more the online structure and storage space that holds the Wii U back. Destiny, as a game that plans on lasting years through expansions, will no doubt needs tons of storage space, which the Wii U simply doesn't have. Also, PSN and XBL are simply miles ahead of Nintendo's network, and the network is very important for a MMO.
You're Gonna Carry That Weight.
Xbox One - PS4 - Wii U - PC