Why Im getting sick of ranked...

Recently I've gone on tilt and dropped back to bronze from silver, so I decided to get my sh!t together and climb back out but I just got done playing a ranked game with Ezreal that I lost. I ended with a k/d of 17/8/8 and 205 cs against Graves, my biggest counter. Nami and I completely wrecked bot lane, but I STILL can't win, I don't get what I'm doing wrong. If I can't win or carry when I'm playing damn near as good as I can with my best champ at my best role then I don't think I'm ever going above silver and feel like I should call it quits with ranked and just stick to normals. Any tips or pointers on why I still fail to carry even with those stats and complimenting my team and not flaming?