I think the bigger problem is the NHL has changed since 2004 and not for the better
this is definitely not it.
I think Canada is diversifying. And the generation of people who loved the Leafs because they were the only game in town for everyone in English Canada are just straight dying off. A kid in Saskatoon can cheer for the Jets or Flames or Oilers or Capitals or Ducks, or they could be hooked on baseball or basketball... in 1965, your only option there was to follow the Leafs.
The NHL has literally never been more popular than it has been post-lockout. Canada is just transitioning to be more like the US than it was 20-30 years ago.