I wouldn't really say that is accurate about bronze players.. Maybe partially?
Basically the idea is to be really good at 1-3 champions so that you can.. Focus on learning the game vs learning the strengths of your champion in relation to the other 9 champions on the map. So ultimately, you should focus on that part first.. Then you can more easily learn "the game" if you will.
How do you learn how to play League versus just knowing what your champ does? How do you gain game knowledge?
Once you learn the strengths and weaknesses of your champion to at least the level your rank is at or slightly better. You can start to see windows (or should) of opportunity. Once you start taking advantage of the enemy's mistakes and poor map coverage/objective control, that is where you step in. Every missed opportunity is to some degree, a mistake. The team with the least, or "less severe" mistakes, generally wins.
TL;DR use the experience you have with your champion to punish the mistakes of your enemies via objectives.