Retconning never should have occured
Its a shame that the League was retconned. Not a big surprise in the slightest. However its facepalm worthy even more when you think about the fact that the League didn't need to be retconned away.
Storywise just have the League slowly fall out of favor with Runeterra. Politically slandering their reputation through the mud, sabotaging the League via external factions, putting champions like
in danger when outside Summoner's Rift. It would never be a single explosion that took out the League or an army. Its the fact that the League was a necessary and neutral faction to the peace of Runeterra amongst the goverments of Noxious, Zaun, Demacia, Bandlecity, etc.
RIOT stated countless times how "The league is so constraining to future characters" that this would have been the perfect opprotunity to also kill another bird with a single stone. Which bird? The fact that for a long time the lore was removed and nothing except a footnote took its place.
BOOM! Suddenly you got all these characters who were with the League who now suddenly don't have a League to go to. This allows for character growth amongst SO MANY different champions as they now must live within a world where the League does not exist. How does this affect the rest of runeterra? What do the champions do in this new and strange world, one without a league? Have certain nations like Noxious went back to their old ways? What new beings have reared their head because the threat of the League no longer is as potent.
I can tell you easily how Summoners maintain their place within Runeterra and its very simple and still allows for places like Summoner's Rift and other places to exist. The answer is: What was once a large neutral faction becomes an underground cult/faction. For they believe it is the best thing to try and maintain this power over these characters for the better of Runeterra. BOOM! You still maintain all the Summoner stuff in the game like how there are "Summoner Spells" and your "Summoner Level" and how the champions talk to you and refer to you as "Summoner" and how there is "Summoner Icons".
See what I am talking about? No retconning needed to occur when regarding the League itself. The fact that they retconned one of the BIGGEST PLOT POINTS is why I question what their Lore team is honestly thinking at times. As they had a win/win sitting in their laps and didn't notice it at all is to me what it seems.
How is it a win/win? Easy. RIOT gets to free themselves of the League and no longer feel "constrained" by it. The fanbase wins because the lore isn't retconned and instead it would have been expanded upon based on "The Fall of the League".
I know its late for this opinion but I honestly thought it had to be said as I am a person who enjoys writing stories and analyzes the stories from a variety of franchises that are often on a variety of mediums.