People say breakaway speed is not needed when they have been conditioned not to expect it based on the team's RB1 who doesn't have break away speed. Ask Philly, Atlanta, Baltimore, Detroit, SF, NJ Jets, Indy and Cincy who all have RBs with breakaway speed. All of these team's added a RB with breakaway speed as their previous ones didn't have it. Breakaway speed absolutely matters.
NFL defenses are better equipped to stop big plays but it’s good to have a player who can take it the distance when the defense gets caught out of position. Someone like Gibbs is a perfect example. Adding him took the Lions to the next level.