There is something called GOLD PER MINUTE, when someone carries your team hard it is because they have a very high amount of gold per minute from farming, CS, and objectives.
Typically bronzes and silvers have around 300 per minute, Diamonds have 500+
The big mistake many of you bronze and silvers make is you win your lane 2-3 times and then you go help the loosing lane all game. Guess what, your now sharing your Good Gold with Bad Gold and averaging it out, not a wise Idea.... You are LOOSING YOUR ADVANTAGE, same for junglers, dont spend all day ganking bad lanes.
Team fights are good but many times unnecessary. You should check your lanes and see how far the enemy minion waves are to your base in each lane before risking your team getting aced.
Team fighting when the enemy team has an advantage is dumb luck...
Also, You DO NOT NEED TO RUSH BARON, if your lanes are all pushed towards the enemy turret. Take this opportunity to get objectives. What good is a baron going to do for them if the waves arent near your turret.
PLEASE START LEARNING
PS. Your team will shit talk you, tell you youre a bad jungler, team mate etc. DO NOT LISTEN TO THEM, mute all if you have to