Remove Solo Queue.
A lot of people are going to be angry or upset at this suggestion. However, it is 100% the best thing for League of Legends.
Solo Queue right now is meaningless. Bronze players say so, Professional players say so. Everyone understands this. Solo queue means nothing for competitive league of legends. So what does it do? It provides a place for people to FEEL competitive. Whether or not this is a positive thing is up for debate and not really something I'm interested in discussing.
Why keep solo queue? What purpose does it serve? To compare ourselves to one another. There's no prize pool to acquire. There's no trophy. There is literally no reward at the end of the tunnel beyond being able to say "I'm better than you" or "He's better than me". Pros understand this more than anyone, since they've REACHED the end of the tunnel. You may say that is what competition is about, but it's about more than just "I'm better than you".
How does comparing ourselves to one another promote a healthy community? It causes us to look down on those less skilled than others and promotes an unhealthy obsession of "climbing the ladder". We get angry at people who simply don't play at a level that meets our expectations. We get upset at trolls primarily because they cause us to lose ranking. It's gotten so bad that many, many people refuse to even dip their toes into the ranked ladder, for fear of ridicule or hostility.
Removing solo queue and replacing it(not just providing the alternative) with an unranked draft will drastically reduce toxicity, allowing people to still play the same game mode they've enjoyed in ranked for so long, all without the negativity, AND pressure, that comes from a solo queue ranked ladder.
LoL is a team game. By promoting solo play, you are pushing people towards a style of play the game wasn't designed for.