Not because i think it sucks or anything (I'll leave that to the mains to determine), but because it establishes that there's no afterlife in the LOL universe. No heaven, no hell, just the Fields of Asphodel and despairing entropy. Your body's death is just the beginning of your true death, of your soul's undoing.
Why does it have to be so grimdark? Why is the only light or "hope" for an afterlife some evil asshole trying to build a castle out of people? None of your favorite champs will rest easy in the end. Not Sion, not Ekko, not Miss Fortune, not Urgot, not even the kid that Janna gave a hug. And Yorick will be really, REALLY freaking sad 'cos it turns out he couldn't save anyone and all the souls he set free are just destined to fade anyway.
The League universe goes out of its way to always offer SOME hope, even if it's soaked in (imo too much sometimes) blood. But even that is gone now, it seems.
Couldn't there at least have been some sort of token reincarnation thing like the river Lethe from the greek mythos (Drink and you will be born again. Drink more and you will be born fortunate but lose what wisdom you have earned. Drink less and you will be born unfortunate and retain some wisdom)?