That point about how all the other black characters in League are defined by their struggle is one that I've never considered. Yes, character problems drive growth and create interesting story opportunities, but that doesn't mean that's all they have to have (nor does it make the ones that do bad characters by any stretch of the imagination).
I'm an African-American kid who's grown up around stories where very rarely do people who look and talk like me get to be the protagonist or hero just because, especially in fantasy and fantasy adjacent settings. K'Sante is a well crafted and interesting character beyond the color of his skin of course, but when you add that in the first feeling I get is "See! People like you are welcome here! You've got every right to exist in this place." It may seem trite or unnecessary to some but I can't tell you how much I wish I had this type of character to identify with growing up.
Representation matters.