Pros and other high level players don't "randomly decide" something else is good. They respond to changes patch to patch, play thousands of games to test what works well and what doesn't, and adapt team strategies accordingly. They don't just get tired of playing OP champs, they seek out the next OP champ based off of changes made to the game.
That said, I'm talking about players who, if they played an off-meta champ, would almost always lose, because they're competing against other players who would stomp them with stronger (meta) champs. At most elo levels, there's more leeway and players can be good/effective with any champ; or at least a large variety of champs. But you're right, a lot of people are meta slaves/only do what the pros say/do.
On a pro/high elo level - Yes there are champs that are just outshined by others
At lower-mid elo - Meta champions' power levels can be overcome more easily (because people playing those champs are probably only playing them because they saw Bjergsen playing them)