In every professional game there exists a meta, now this meta can be more or less important. The more important the meta, the bigger the gap between something viable and unviable. Therefor in order to give the game the biggest diversity possible the gap must be very small.
In an optimal, balanced scenario, that will never be reached, but is still important to try to reach, everything in the game is viable and the player makes the difference and not the champ.
This however is not what the balancing team seems to be trying to do. A meta is created artifically by making some champs strong, while making other champs weak, basically taking the weak champs out of the game.
This is my point. I do like the game and I enjoy it, but I would enjoy it so much more, if it had more diversity. It could have this diversity if it was more balanced and therefor unlocking all the unviable champs.