At this point mediocre won't do. I watched two well established, i.e. long in the tooth, TV shows last night with major musical guests. Despite the hard work and energy expended, they both bored me to death. Oh, I don't care if they practice in front of a mirror at home. Onstage, though, I need "real."
Little Richard was born Little Richard even if he didn't know it. Bob Dylan had to learn to be authentic. He built a mystique. He developed charisma.
In most cases, old and new, your favorites and mine just might not line up. That's okay. If you don't like Elvis, circa 1956, though, you're just wrong. In fact, you're dumb.