There’s an old Yiddish proverb: You can’t dance at two weddings. At some point in life, a person has to establish a hierarchy of priorities, in which you do X but have to give up Y. That is why, despite the life plans of many preschool-aged children, it is exceptionally rare in society to see combination fireman-astronaut-ballerina-cupcake bakers. You can’t do it all.
In soccer, it’s the same idea. In order to press the attack in one place on the field, a team must yield territory in another, becoming vulnerable on defense, and vice-versa.
Under Pablo Mastroeni from 2014 to 2017, Colorado prioritized defending above all else, keeping all four defensemen and two central midfielders back in most situations, and hoping to get a goal with just four attackers — or in set-piece situations in which the ball starts at rest and in an advanced position.