BS Matchmaking

Can anyone for the love of god tell me why I go on win streaks or lose a game or two and each game I have silvers and atleast one bronze or unranked player on my team? while enemy team always has g3 or g2+. Really pisses me off and it's very discouraging knowing it's over once it start. Even when you try to help everyone and help take objectives. Very frustrating that I'm stuck with this.