I would recommend focusing on your positioning and CSing abilities. Play smart. You can't win them all, but you can try to play to the best of your ability. Focus on map awareness and just play smart. Try to get as big as a lead as you can during laning phase then try to group up and make some picks/push objectives. Bottom lane usually has most control over dragons so if you can manage a kill in bot lane and the jungler is near, try to secure dragon and push down towers. Sometimes you lose no matter how well you play. Positioning during team fights is huge though. Just keep playing and try to get better, don't get mad at your team, it just makes it worse. Mute them and keep playing. Try to improve as you play, see where you went wrong and how you can fix it.

Try adapt to the enemy play style if there reckless you need to take on that and let them jump in and then 1v? them with your team, if your playing someone that's not to clever you can lead them into ganks and ambushes. use the surroundings to your advantage and dont get caught chasing the 1v1 as you will end up getting ganked badly.

You're here complaining that you dumpster kids in lane and then cant win game? You're playing Vayne with exhaust, what do you expect? Be clever when in champ select too.

I found your problem. "When I play norms"
No. If you want to play you don't play norms. The reason you're playing against those ranks and doing well is because they're norms. Norms are simply for messing around, trying things you don't normally play, and perhaps multitasking. In normals I play against at least 3/5 diamonds each game. In ranked I've only made it to gold.