I think ranked play needs a try out system. Either you get in or you do not.

Bronze is basically the cesspool of everyone who plays either for fun, or just aren't that good at the game. Bronze can also hold back people who might be better than the average person. I do not intend to say that these people are potential for challenger, just saying that bronze and low silver tend to have a group of "either you win heavily, or you lose heavily". I don't pretend to know how the matchmaking system works, but it feels very luck based on which people get casuals and which get people wanting to win.