Death is a strong word, but steady decline absolutely. There are a lot of reasons IMO as it is a complex issue impacted by economical and social factors
Off the top of my head, here are a few:
1- The newcomers prefer soccer. While immigration is a federal jurisdiction, Quebec does have a hand in the criteria to select immigrants which include the language spoken. A much higher proportion of french speaking immigrants go to Quebec (duh) and, in a lesser measure, Spanish-speaking and Portuguese-speaking. People from France, the Maghreb, Belgium, Western and central Africa, Brasil and Latin America overwhelmingly already have a sport, it's soccer. Hockey won't dethrone it in their hearts
2- The greater Montreal doesn't care about hockey it's not affiliated to the Habs in some shape or form. Despite a urban area of 4.5 millions people and it being the economic engine of the province, the greater Montreal only has ONE QJMHL team, the Armada. Let's get real, hockey is a rich suburbanite sport and the East and West of the Island, Laval and both shores are peak suburbia with a lot of wealthy ones sprinkled in. The fact there's only one QJMHL team is really telling
3- Mothers don't want their children to play hockey. In my experience, the leader of the household in Quebec (or at least in the greater Montreal), which includes the children activities, is the mother. To say male minor hockey has terrible press among women is an euphemism to say the least. There's the Hockey Canada scandal of course, but also the recent cases with the players from the Tigres and Voltigeurs. Then you add the risk of concussion and hockey is undesirable sport for parents at the moment
4- Hockey is hella expensive. Quebec is not as rich as Ontario or Alberta and it's even more accentuated outside the greater Montreal and the Quebec city region. Having a kid play AAA is just so expensive
5- Hockey Quebec and Hockey Canada are viewed as crooked and incompetent. I mean...
6- Hockey parents are seen as trashy. Ask any hotel staff, they'll say hockey families and coaches are the worst and some hotels even ban them, It's way more minor than the other reasons above but still. Hockey really has an image problem
7- The culture of volunteering is at odds with the cash grabbiness some teams exhibit. It's not a hockey specific thing though. If you feel like your son's team is trying to make you pay for every single thing, you might not be willing to help them for free. A strong network of volunteers is the backbone of any sport
This could change though, the PWHL is doing a lot for the image of the sport and if the Habs win a cup it might reignite the passion. On the other hand, if the current rebuild fail and Canada can surprise at the upcomming soccer world cup. The latter might overtake it completely in Quebec