The big issue is that the PQ hasn't really had a huge representation even among the majority-francophone population. That's why they've lost each separation referendum; there just isn't the popular will to see their policies put into effect.
I mean, I have issues with their language-protection policies over and above the separatist agenda, too; I understand they're worried that English would "creep in", but it's gonna do that anyway, and you end up with a culture that's antagonistic to English in strange ways, ways that don't exist in the other direction outside of Quebec, either.
If they took a stance based more on Quebec the province, and less on French the linguistic cultural identity as expressed as an antagonistic distinction to everyone else, they'd be more successful, IMO. That's why they get very little support outside the Francophone community; they don't have much if anything to offer them.
More realistically, I don't see why they have a role in
national politics. Provincial, sure. But national? Makes little sense.
It's less that, and more that they don't acknowledge certain legal facts. For one, they often don't want to admit that Labrador is part of Newfoundland, not Quebec. Not all of them, but enough that this is still a "thing";
http://www.cbc.ca/news/canada/newfou...order-1.639001
For two, the last major separatist referendum, it came out that the Native peoples of Quebec still had official treaty rights to much of the land in Quebec; it was never formally acquired by Quebec or Canada. So, as Canadians, they're part of Canada, but their lands are
theirs, not Quebec's.
The whole thing would be a giant nightmare even for separatists, which is why it never really gets off the ground.