Why do all of my teammates play so bad? I can never win.

I play this game a lot (basically only qp) and i am almost NEVER having fun because of 2 things: the enemy is always extremely good and my teammates are always extremely bad. I am completely serious when i say i am almost always the only good player on my team, completely carrying and still not being enough to carry 5 people to victory against a cracked enemy team. I legitimately am starting to develop problems because of the anguish and despair and helplessness these matches bring me, where no matter what i do, and how good i play, i can almost never win because i cant play for an entire team. PLEASE if anyone has any advice regarding anything that could help me, it would be greatly appreciated. I am at a loss