It seems like Riot is saying: "We don't want to make a story that fits the game. We want to write a fantasy universe off to the side here. That game you're playing? It's a meaningless mashup of what it might be like if for some reason these characters started fighting each other."
I don't understand this decision at all. The great strength of the League of Legends as a lore concept is that it quite conveniently explains where we the players fit in, and where our matches fit in. Before you say, "Oh, you're Champions now, instead of Summoners" — that's not really true, is it? It's more like, at best, "you're now Champions fighting non-canonical brawls in some kind of arena for some reason." It's more like we're playing daydream fantasies of Champions, doing things entirely divorced from what they might actually be doing.
I really don't get why they felt they had to erase the League to write their "exciting new stories". By its very nature, it's accommodating of all kinds of plots.
Want to have a war? Sure. The League's job is to prevent the planet from blowing up, not ensuring world peace. So the war happens, with the League simply setting boundaries on how far the conflict can escalate, and eventually declaring a winner.
Maybe they're expecting to write the next Game of Thrones. With all due respect, I don't think they're going to pull that off. It's a shame that their pursuit of this objective leads them to treat the actual game League of Legends as a secondary concern.