I don't have much of a dog in this fight, but I think this point of yours is worth emphasizing: for a whole lot of reasons, Canada is not going to limit access of PR-sponsored parents to health care, old age support, or most other benefits.
Some people recognize this but many don't: that's an ENORMOUS liability the government (actually multiple levels of government) are adopting - with, for the most part, those parents paying little in the way of ongoing taxes that probably - for the most part - won't be met by their sponsoring children either.
Some will claim their parents do/will pay taxes, that their own taxes will compensate, they won't make much use of health care, etc, etc. Well, maybe - but it doesn't matter because statistically the sponsored parents can and might make use of them. Canada is not going to limit access to these benefits if they're needed.
Therefore the selection has to be limited somehow to modest numbers: by money (like Australia), by lottery (like now), or by some other mechanism (feel free to propose). None of them are going to feel 'fair' to everyone.
Right now, with problems with health care access and a shortage of housing, it's going to be even less popular. That's why I say I doubt there will be another lottery before the next election (and who knows after?): it would be another political punching bag that the current governing party doesn't need.
[Note, overall I think this program has less party valence than many think. Conservatives will probably have some program for parents, too, just perhaps more limited or more restrictive somehow. I could be wrong about that - but I guarantee if Libs introduce another lottery, the Cons will attack it mercilessly.]