One thing I noticed that LH does on my recent 6 flights with them, that AC never does, is respect the boarding time. LH sometimes starts the boarding process even before the posted time, where AC seems to always wait untill the last minute. I believe this is part of the issue. Another, may just be how they schedule ground crew... perhalps they have the same last minute approach to getting the luggage and cargo on board. On a recent YYZ-YOW we where 40 minutes late leaving as the captain informed us multiple times, I still have the main cargo door open. I watched them arrive with the last container at T+30 minutes and put it in. Not sure what billiant tool couldnt wait for the next flight which at that point was only 30 minutes away...
Perhalps if Airports in Canada where more harsh on the dept/arrival slots and finned AC for every late arrival and departure; they would actualy set this issue as a priority and find out what is causing so many delays.
However, with the company bleeding cash like it is, I think they have other concerns ATM; like finding new ways of pissing off its passengers and staff.