So has our team's defense been better this year?
Yes, it has. Our defensive metrics have improved, and our expected goals against has gone from 24th in the league to 16th.
Unfortunately, many believe that "defense" consists entirely of "stopping the cycle". While this is important, and something that the Leafs are probably below average at (though not to the extent that some people think), most teams struggle with this and defense is about so much more. It doesn't do you any good to stop the cycle, if when you get the puck, you can't get it out of the zone. An ability to maintain that possession, make crisp passes, and get the puck out of the zone is crucial.
We used to get stuck in our own zone for incredibly long stretches and bleed chances, because every time we'd get the puck back, we'd make a bad pass or throw it blindly up the boards, either for an icing, a penalty, or a turnover.