i would trust win rate over bronze analysis in terms of balancing anyday
bronze level balancing is the reason why champions can have sub-40% win rate, those champions already had low win rates to begin with and people cry they are op and they go from 45 to 40.
just like in ranked where winning and losing is the only indicator of skill, pure numbers should mostly be decided for balancing instead of bronze level balancing where something has no counter play yet it still loses significantly more games than it wins. if you're a statistics major like me you understand why elo is actually the best estimator of skill possible (without looking into games) , win rate is also the best indicator of champion strength without looking into the champions kit.
that said, obviously we can look into a champions kit and analyze how strong that champion is, but it takes people who truely understand the game to analyze it properly. I can easily say if you have any modicum of game knowledge, you should easily be master/challenger with 0 mechanics.
if you have 0 game knowledge, then win rate is all that matters. enemy pick lee sin? you already have a 55% chance to win the game. enemy pick sejuani? you already have a 42% chance to win the game. you have no idea how to counter strengths and weaknesses of champions.
let's say sejuani is balanced 100%, if you guys knew how to counter play against her it should drive her win rate right down to 50%. her win rate sits at 58% so there can only 2 conclusions. our original assumption that sejuani is balanced 100% is incorrect, or most people who play this game have 0 idea how to play this game. people are not going to stop being bad so it doesn't really matter.
same thing with lee sin, you can say that lee sin has a low win rate because most people who pick him are bad, but does it really matter if he's op if people are going to continue being bad and he continues getting a 45% win rate?
im actually very happy when my opponent picks low win rate champions, i know in the long run its just freelo to me.