Too much throwing in competitive

I'm plat 3 and can't get any further due to getting in games with throwers and leavers constantly, why is it like this? Earlier I had a game where I hovered as lord rocket and someone on my team banned rocket, we still somehow won and it's probably due to my 42k healing as cnd. Then I got in another game where someone on my team hovered daredevil and another person on our team banned him, then went black widow and went 8-16 and refused to swap. Another game I had a leaver who left when we weren't even losing. It's just so frustrating, and reporting these people seem to do absolutely nothing.