The PhD taxi driver isn't a huge problem because it's voluntary on the part of the immigrant and usually those people send their kids to top universites.
Of course it isn't voluntary. If you had a PhD would you prefer to work as a taxi driver?
It's a mix of multiple factors:
- Some masked racism (usually in form of "needs Canadian experience" meaning for most people: either you spend some time in a cashier/cleaning/etc job or you aren't getting through to us)
- Curriculum stuffing/PhDs from some smaller countries might not be worth the paper they're printed on (which should be easy to sieve in an interview - but a Canadian won't go out of the way to help you - not even a bit)
- Peculiarities of the Canadian job market (centralization depends on area/specialty, etc)
I recall the last PhD taxi driver I had when discussing this had their PhD in “Geography”.
PhD in Geography could mean a lot of things but among those the chance that it's a fluff degree is high I'm afraid (and it might not even be a PhD)
People running away from war and famine have a different humanitarian immigration path into Canada which is not built with the expectation that they will become net contributors to our society.
Or at least, not in the first few years of their stay - there is every reason to expect them to become net contributors in time, it just might take a few years longer than the point-based immigrants