Fox decided to retire "American Idol," then experienced remorse when ABC stepped in to acquire the franchise. Yet the network's attempt to fill the void, "The Four: Battle for Stardom," is an uninspired addition to the singing-competition genre, with as much "American Gladiators" in its DNA as "Idol." Featuring Fergie as host, and a panel of judges headlined by Sean "Diddy" Combs and Meghan Trainor, the show labors to create tension points throughout.