It all makes sense now
After looking at the graph Riot had on their "No more Solo Q" article, I now understand why ELO hell exists. Pre--made teams have close to a 55% win rate and solo players have close to a 45% win rate.
I always wondered why I could beat Diamond players most of the time. It's because most of them were carried there. I now understand why some of these Bronze players are really good. They belong in Plat/Diamond but are held back by the system. As a solo player you have to be 10% better than pre-made players just to advance at the same rate.
I know I'm going to get flamed hard for speaking the truth, but truth hurts.