it would be a bit odd for Arcane to not touch on it at all if we are a shared universe.
Arcane doesn't touch on the ancient goddess who protects and watches over the cities. It doesn't touch on the cyborg spymaster manipulator who has controlled the cities for decades either, in fact it directly contradicts her existence. It doesn't touch on mutated rats or deliquent doctors.
It doesn't touch on those things because stories need to focus on what matters to them emotionally and storytelling wise.
If Riot's perception of PnZ and the world is purely based on what Arcane shows then I weep for the future of the setting.
Fairly siloed.. off on his own.
That just means you could have fleshed out why the Brackern were so powerful to begin with or in what ways they may be important for Runeterra as a whole. If their crystals can warp time, what does that say about them? What if they guarded the world runes? Suddenly you have a much more urgent angle to Skarner trying to mend them.
He could have been tied to a dozen different champions in a dozen different ways, while retaining his angle of "impending Piltovian reckoning", just like ASol is for Targon, just like Mordekaiser is for Noxus, just like Kayle is for Demacia, and many more. These things never stopped you before, but they stopped you now.
His new background puts him at the center of political struggle of a region.
I appreciate new Skarner, I just find most of these arguments nonsensical. Not every champion needs to be some riveting inspiring story.