I just had a game that demonstrates how much of a problem this is.
I'm Vel'koz at mid against Ekko. We're both 1-0.
We traded 4 kills for 4 kills at the first dragon.
Everyone on my team gets one kill, while Ekko gets all 4 kills and shutdown gold.
The end result is that I come out with +300 gold, while Ekko comes out with +1400 gold. Ekko now has his entire first item and a stacked Dark Seal, while I only have Lost Chapter.
The game is completely over for me. Ekko can almost one shot me if I leave my turret, because he has such a huge advantage. He's free to do whatever he wants and I can't contest him, allowing him to go to other lanes and snowball out of control.
This basically boils down to the game being lost for my team due to happenstance. His team didn't strategically give him the kills, he just happened to get the killing blow on them, and didn't even contribute the majority of the damage. If he hadn't gotten all of the kills, the game would have continued roughly even, with both teams having traded evenly at that dragon, as it should have.
Fix this. Distribute kill gold from team fights better to stop one champion from snowballing off of a single otherwise even team fight.