It's really not "OP" or "Overloaded" Champions costing you wins, it's most likely your choices

The next time you're in a normal or ranked game, really pay attention to the mistakes you or your teammates make. Pay attention to all the pointless risks that are taken, or all the badly thought out initiations.

I played a game with a seemingly good team composition, but my team decided to invade the enemy jungle and conceded 4 deaths before the 5 minute mark was up. Most of the time it's not champions having an advantage. It's a lot of bad choices and lack of forward thinking.