I don't really have that issue. I honestly think that you are what keeps you from winning. On literally every single champ you have, you have an average KDA with more deaths than kills. On every champ except for Karthus and Lissandra you have more deaths than assists as well. You also have extremely low cs. You would win significantly more games if you'd secure more cs for yourself, and if you would not place yourself in danger as much. Even if your team does badly, that's no excuse for you to not know the limits of your champ at that moment. It's important to know when to fight, but it's 20 times more important to know when not to fight. The skill of an individual on a specific champion has much less impact than these things do on a game. Where skill level comes into play is when you have two people who understand the core mechanics of the game itself equally. Then it comes down to who outplayed the other. Especially in bronze, you can win by just alt laning to a tower, going home, then pushing another lane to a tower, then leave, and so forth. Most people don't understand when to let things go, and will just run around the field like idiots. This works less the higher up you go. Either way, the single most important thing to remember is that you shouldn't hate your teammates for losses. After all, based on your stats I'd say that you probably don't know the champs you play all that well either (you can get mad about me saying that or not, it's up to you, but I'm being real with you). There's more to this game than "I can kill your champ with my champ".
Also to be noted, I've never played
in anything except ranked SR games. I may have played him in ARAM once. I bought him on a whim, picked him on a whim since the enemy countered every single top laner I play well so I figured why not try the tree since I was screwed anyways, and carried my team hard. I have since then played him several times, each time only playing him in ranked because now it's kind of my thing I do with maokai. Last season I had 100% win rate with him. I also play tons and tons of Miss Fortune and Tristana. My ranked stats with both of those have never been anything but awful. Seriously, they're my "I feel like a guaranteed win this game" toons in normals, and have been for a long, long time. For some reason, I always do absolutely awful with them in ranked to the point that I pick them only in extreme cases. So no, how much you've played a champ before taking them into a ranked game doesn't affect it near as much as people stress about it. People just desperately search for any reason to say that they aren't why bad things happened to themselves.