The votes were tallied, the envelope was opened, and after a series of dramatic pauses, Ryan Seacrest finally read the winner’s name aloud and crowned a new “American Idol.” Quick, without looking it up: Who was last year’s winner? Or the winner before that? Let’s make it even easier: can you name a single “Idol” winner in the past 10 years? The American institution known as “American Idol” kicked off its 20th season on Sunday night, but it’s been a long time since the show has had any kind of stranglehold on the country’s attention. There are several reasons why. One, there are too many shows…