Popularity never last forever. That's been true for every #1 show from the start of TV history (I Love Lucy, M.A.S.H, The Cosby Show, Friends, etc). But Idol had a longer & more successful run at #1 than any of them. And it created more superstars than any of its imitators (or predecessors).
If the time has come to end the show, then so be it. But its accomplishments & its legacy will never end. I doubt that The Voice will still be on national TV after 15 years with over 1/2 of that time at #1. Job well done & good luck to all who've ever been a part of this historic journey.
..."Karen, dim the lights."