A list of factors that partly explain the OP:
1) The basic skill level in the NHL has went up immensely in the past twenty years and Hockey Quebec hasn't followed suit. The organization is archaic and in a sad state of affair. Everybody else in the world seem to have upped their focus on forging better young players, though. There are more and more gifted prospects from the US, for example.
2) There used to be a time when goaltenders made in Quebec (tm) were ahead of the others, but I believe that everyone else have learned from goalies like Patrick Roy and Martin Brodeur and that they've moved beyond. Like apprentices that learned from their masters until they irremediably surpassed them.
3) As others have pointed out, parents do not send their kids into hockey as much anymore here. Other sports are favored, because hockey comes with monetary constraints and higher risk of grave injuries.
4) It is also possible that we are in a lull as far as extremely gifted Quebecois hockey players are concerned. There's bound to be some again eventually, even with a smaller number of kids from Quebec playing hockey.
When a team is brought to Quebec City again, and the rivalry between Quebec and Montreal is revived anew, more local kids will want to play the sport again.