Sure it can help to have a balanced roster, but it’s overrated and here’s proof:
offense 1: Qb gets 4 TDs a game and Rb gets one TD per game,
offense 2: Qb gets 2 TDs, RB gets 1 TD and backup RB and Fb combine for 1 TD a game
you may think “oh offense 2 is better, more people getting the ball, harder to stop” But which of these offenses scores more points? Offense 1 does.