I don't think the stretch pass is the problem, sure it's "easy" to defend, but the thing is that the other team has to give up a lot of offensive pressure to do so. The Isles shut down our offense, but it's not like they dominated the play, they benefit from lucky bounces / bad goaltending.
When teams play defensively against us like that, the outcome depends more on goaltending and luck than in high event games, but in the long run the Leafs should still win a pretty good percentage of these games. I have no doubt we'd win a 7 game series against the NYI as long as we had Andersen.
Also, other systems are arguably even more easy to defend than the stretch pass, and not necessarily well-suited to the talent we have. I'm not sure we want this team playing a system where they move the puck up the ice slowly as a 5 man unit and try to grind out chances in the offensive zone. That doesn't favor our speed and skill, it significantly increases the likelihood of injuries, and might hurt us defensively.
The stretch pass is as much a defensive system as it is an offensive one, since it makes it hard for the other team to get odd man rushes, and forces them to dump it in more and take more low percentage shots.
It does feel like Babcock should be able to get more from this group though, we seem to have games like this where we come out flat a little too often.