No it doesnt mean that at all. You also have to keep the puck out of your own net. So what if you can score 4 goals a game if you bare giving up 5.
I'll remind you that the Caps won the Cup because they played a strong defensive game throughout the playoffs. If you remember the regular season the Caps were very inconsistent. Especially in the defensive zone. If we continued playing that system we would have won absolutely nothing.
The same goes for every team. You're forgetting that everyone is on the same level sheet of ice in that regard. Everyone has to score and play defense, it's just a matter of who does both better WHILE scoring more. You still have to score more than the other guy, no matter how good you are on defense. Everyone faces this problem.
Other than the popularization of the trap in the mid-90s and the explosion in goalie equipment size/techniques later it's never been about defense. Advancements in defense are always reactions to problems created by the opponent having too much offense.
You try to find ways to break the defense with offense and not let in more than you score. That's it. Everyone in the league knows every game can't be 1-0 or a 0-0 shootout, so you don't waste your time trying to achieve that. You try to score as much as possible and force the other guy to stop you. He's doing the same thing.
Do you understand? It's not a race to zero goals. It's a race to as many goals as possible, with damage control. IN THEORY. In practice there are coaches who will preach defense and sit on a one goal lead no matter how many times they blow it.