too many cooks spoil the broth

Too many cooks spoil the broth is a phrase which means that where there are too many people trying to do the same thing, they will make a big mess out of it. The idiom is extremely similar to there being too many cooks in the kitchen and when used figuratively, means virtually the same thing. No matter the situation, when there are a lot of people all trying to do one thing, whether a basic or complex task, that only increases the chances of something being messed up.