Don't be sorry.
No I don't think great defense will win you the game, but it will cause the other team to lose.
I think of footy as a bit of a race. The goal is for the other team to get tired first so that their defense starts cracking and they can be attacked. The philosophy of winning games on attack misses this factor completely, as it's all about being so great on attack that you can score at will. But the reality is it's very difficult to score against a well drilled defense unless they are struggling to keep up with the play.
When you focus on Defense first then you naturally focus on fitness, and you also understand better the things you have to do to break the oppositions defense, ie: running them ragged and drawing them into a positional error. So in this way footy is like checkers. You move them around the park until they become tired, and then you move them sideways until they leave an opening to exploit.
If you think of two boxers fighting with one being way fitter than the other. The less fit boxer will be anxious to land a knockout blow before he runs out of steam. That's the same as a footy team that's not as fit. They will want to win early with blistering attack, and not put too much effort into defense.
So I'm very happy that the club has a defense first approach. They need to keep it up as far as I'm concerned, and let the attack grow naturally off the back of it.