Problems with Aurelion Sol's lore/backstory
Disclaimer: His full lore hasn't been released and it may solve everything.
A few years ago we have nasus, he comes from some super advanced alien world and has such extreme power that the entire world begged for his mercy, cut to him being shot to death by a blow-dart.
His lore was updated and his power-level was reduced to that of an ascendant and any mentioned of a whole civilization created for just one (and later 2) champions was removed.
Now we have Aurelion sol. Who is by far and away the most powerful champion (he can MAKE STARS) enslaved by a civilization that can travel between world and has the power to enslave a cosmic being that can CREATE STARS.
So power imbalance will always exist in LoL there is no denying that, but at least everyone was within a similar range, a range that aurelion sol blows out of the water, this is kind of unfortunate but somewhat inevitable, but I still think that he could have just as easily been a manipulator of cosmic energy instead of a creator of stars, or maybe the celestial of the heavens part of the same pantheon as kindred and bard but whatever.
My real issue comes from the introduction of an advanced race of beings so far removed from what is considered cannon within the League of Legends universe that they probably have the ability to wipe runeterra and every champion out of existence. Not only does this completely throw out of wack our perception of the lol universe but make every lore question pale in comparison to what is that civilizations goals, what are they doing, how can we defend ourselves against them (see Stargate).
I don't really care about who VI's sister is or who zed really is when there is a space-faring civilization, or even the capability for one to exist if aurelion sol wipes out this particular one, that could be a danger to everyone.
LoL lore is essentially a character driven story and this makes it into one more about circumstance and what is happening than who.