First thing is fix your mentality. Stop blaming your team for your losses, and stop patting yourself on the back for carrying.
The only thing you can effect in your games, and the only constant is you. Focus on improving yourself. Looking at your match history, it's not uncommon for you to die 10+ times in your games. Try to look back at situations where you died or where something happened and think "how could I have done that better?"
If need be, record your games. replay.gg will record your games and basically let you go back and view them as a spectator. or plays.tv will record exactly what you see on your screen. That can show you if you need to improve your mouse accuracy, cs (which yes, cs is definitely something you need to improve on), skills shots, dodging, etc.
Learn more about different matchups and what every champion does, and what their possible weaknesses are.
Learn when you should go for what objectives. Should you push your lane? group up mid and help push there? take dragon? learn when to do what.
on the cs thing, just go into a custom game by yourself and try to last hit as many creeps as you can in 10 minutes, and try to improve that number. if you can consistently get around 70-80, you're in an okay spot. not great, but better than most people in your elo. Try to do it with a blank rune page as it will make it a little harder when practicing, but much easier when actually playing.
If you have higher ranked friends, ask to 1v1 with them and get tips on what you could specifically improve on.
It doesn't help everyone, but watch some streamers play or watch videos on how to get better.