You die a lot.
Here is the thing: That teammate that went 0/4/0 gave the enemy less gold than you if you go 13/15/13. Personally, I consider any game I died more than 6 times to a bad game for me. You cannot carry if you are dead - and if you give the enemy a lot of shutdown gold in the process, you are only making it worse.
Furthermore, kills are not important. If that teammate who went 0/4/0 pushed toplane all the way down to their inhibitor, he was more useful than you chasing only kills. Kills do not win you a game. Towers, inhibitors, dragons, barons and nexusses win you games.
And finally, your CS is atrocious. Really, REALLY bad. You seriously underestimate the importance of killing those minions.
So basically in short:
- dont die
- practise lasthitting
- focus on objectives