Choosing a champion for when they're strong, rather then for what they do.
Let's take Vayne for example. Everyone knows that she's often picked for her amazing late game. But should it be that way?
Should she not instead be picked because people enjoy the play patterns of Tumble -> Condemn?
Rather than saying "Okay, we want Nami to be good early on but useless late so we're going to give her high bases and crap scaling.", should Riot not balance her for her kit?
Instead they should be saying things like "Okay, bubble is a little bit too easy to land from afar so we're going to slow down the projectile speed." or "Ebb and Flow is a bit too forgiving with the range of its bounces, so we're going to leave the stats alone but reduce the range to reward her for using it on close groups"