@Riot: Why didn't you annihilate the Institute of War instead of retconning it?

I understand that the writers were having a lot of frustration with the Lore up to that point and how the Institute of War, the League of Legends, was constraining the world they wanted to create. However, was retconning the entire lore really the best idea, both for continuity for players and work load?

Why wasn't the Institute of War utterly annihilated or simply vanished from the world, summoners and all, without a trace?

This would have had the world and lore be mostly in the same place we have currently have, maybe with a short time skip to move the world further forwards, but without the need to retcon so many stories that were connected directly to the IoW and summoners, like Jax, Lee Sin, and Ionian Boots of Lucidity to name but a few.

This also opens up new stories as Demacia, Noxus, Shurima, and all the other city states new and old have to deal with the loss of the major super power that kept balance on the continent for so long and the impending threats like the Harrowing, more and new Void spawn, the Watchers, and everything else as well as each other.

This also explains why Bard has suddenly appeared after being gone for ages. Without the Institute of War to force their balance, the world is shifting quickly towards utter annihilation, who's appearance currently doesn't seem clear or well explained. In fact, Bard almost seems like the Institute of War itself in the from of a champion based on his lore.