Ben was not pegged to start his first year. Only with the injury to Maddox was he able to show what he had. The fact is Pittsburgh didn't design the offense for Ben, but he sure did well with it.
Banks, Bledsoe, Bulger, Marino, Kelly, Culpepper, Garcia, Leftwich, The Mannings, Mcnabb, Palmer, Favre, Plummer all played significant time in their first or second years, and played at or above average. Sure there are planty of others that took longer to develop such as Testeverde, Dilfer, etc.... But they typically did it much later and with a different team.