Lee Sin Will Never Be Nerfed, This Is Probably Why

Simple. He's not the best at everything. He's never been (except for short periods of the nerf cycle, before champs with clearer strengths appear) at the top, always 3rd, 2nd, 4th. , depending on the meta. And that is because he is the closest thing League of Legends has to a Jack of All Trades. Except for short periods of time between meta shifts where no one knows who is strong yet (most still using less than optimal choices, so beats them due to being dependable in that he can survive most changes with a real severe dip in his moderate power, now comparatively stronger/est). Then the champs with clear weaknesses (and strengths) rise up, better suited, and becmoe the actual 1st and 2nd place options, then Lee Sin at 3rd/4th/2nd. If they nerf him, he goes from dependable Jack of All Trades able to weather the strom and do moderately well, too well...suboptimal to the extreme in all meta shifts. No clear strengths (his iconic kick isn't considered, reason why below), and yes, no clear weaknesses, because otherwise he wouldn't be dependable, he would just be weak.

Reason the kick doesn't count: Its iconic because it fits his Jack of All Trades nature, being situational, but useful in multiple situations, and also its damage while high, isn't far out of line compared to other ultimate that deal damage, there's nothing wrong in that area, unless you just want across the board nerfs to champion ults that deal damage.

TLDR: Lee Sin's nature as a Jack of All Trades, Master of None makes him rarely the strongest, only moderately strong, and almost never truely nerf/ban worthy (exempting the rare people who have utterly mastered his mechanics, raising him to the terrifying Master of All status, but also a feat only extremely high elo players can accomplish cough Insec cough). Nerfing him would move him to simply Jack of All Trades, Shit at all of them, comparable to some champion in need of a rework today that will not be mentioned (in fear of angering the legendary mains of this champion that have survived into today's meta ecosystem).