You have no idea what the SBMM does or is intended to do, do you? No matter how good you get unless your the top 10% you will be placed with equally skilled players the intention is to keep your win loss at 50% and KD at 1. If you start beating those metrics you will get matched with better players until your stats become the average and then that's where you will stay. It inherently stops you from seeing improvement because the players your against always match up with your own skill to keep everything average.