I cant carry hard enough

Im now officially the lowest you can be in ranked. A dirty Bronze 5. I personally don't think I'm a bad player. I'd like to think I could be in at least silver where i was season 4. I understand league is a team game so I'm not gonna point fingers or anything but sometimes (more times than not) I get mediocre players who have their lane match up snowball to the point where they oneshot everyone including the tank. I don't really care about that. I just wanna know what I can do after that to potentially win. I've noticed that league is way too hard to solo carry in. So what could I do in my games to help out my team and potentially make a comback.