Im probably in the minority here but I disagree.
Champions like shyvana don't really fit the lore; the lore had to be changed for them. Same with my main, nidalee. She pretty much had no place in the lore which caused them to have to add a new region just for her and like 2 other champions as well as releasing a new champion just so there'd be someone for her to have lore interaction with. If they only made champions based on what already existed in the lore nidalee would never be a thing.
Nothing about demacia in the lore would remotely suggest that a half dragon lady would live there so they had to bend the lore to fit her archetype. Kayle and morgana had their own lore for a long time but it had almost nothing to do with the rest of the lore, so they changed it so that kayle and morgana were aspects and had something to do with demacia or something.
Another example is brand. There's nothing in the lore suggested of someone like him existed so they created him without the lore in mind, and then added him to the lore in the form of ryze's student.
My point is that when they disregard lore, they can come up with unique characters, and then make changes to lore to include those characters. This will cause the lore to evolve based on new characters, and character choices aren't constrained by what's currently in the lore.