Kassadin is now the old Varus
Before completely destroying the identity of Varus and turning him into some kind of idol for the LGBT community, Riot actually had one unique quality trait in Varus' story that set him aside from the lore of all other champions: He was a father. Kassadin's new backstory not only transfers that mantle onto him, but the story as a whole is all too similar to Varus' old lore in that he lost a wife and child and now seeks revenge for their deaths.
To be honest, I was a bit disappointed to read that in Kassadin's new backstory; it's uncomfortable to think that the stories and lore of the champions we love can be so easily interchangeable whenever it is convenient for Riot to make changes. In the future, I hope champions that need story and lore improvements are built on what is already established instead of being entirely rewritten.