Canadians (even those who haven’t registered their citizenship) are required to enter Canada on their Canadian passports. Dual citizens cannot enter on any other passport.
I 100% support your overall point that Canadians generally have to and should use Canadian passports to enter Canada.
But: it's a tiny bit more complicated - because the question of entering Canada is distinct from being able to board a flight to Canada and whether you need a visa and if you don't need a visa (benefit from visa waiver), you still need an ETA, etc. And of course, not all border crossings are by airplane.
This page has some detail:
https://www.canada.ca/en/immigration-refugees-citizenship/services/visit-canada/dual-canadian-citizens-visit-canada.html
Short form: one must never, ever present to a border officer for entry using 'another' passport or citizenship if you also have Canadian citizenship. You MUST state and enter on the basis that you're a Canadian citizen (and nowadays, that basically means a Canadian citizenship document such as a passport).
But: to get on a flight to Canada, you have to show you have the right to enter Canada. For Canadian citizens, that USUALLY means a Canadian passport, and the airlines don't (I think) have to accept your other documents. You can show the airline your Canadian passport if you booked the ticket on your (say) North Korean passport.
And I'm not even going to attempt to explain how this works if you have a Canadian citizenship document of some kind but a visa waiver country passport and whether you can get an ETA etc (I don't know the details and don't want to - I don't think Canadians can get ETAs using a foreign passport). The key point for this is: whatever you say about your citizenship, the airline MAY (and quite probably will) refuse to let you board the airplane to Canada unless you show your valid Canadian passport.
If you actually GET to Pearson airport with your Canadian citizenship card, I don't believe they can refuse you entry. But that hypothetical won't matter to you when you're stuck in Ulaan Bator and refused boarding on your direct flight to Gander (leaving aside that this is a very infrequent flight).
End conclusion is the same as your above, except for proviso in the link about entering from the USA by land: don't risk trying to fly to (enter) Canada without a valid Canadian passport. Not because they'll turn you away at the Canadian airport, but because you may not get there from the foreign airport. (Again, there are some exceptions, but increasingly rare).
(If I've made any error of fact in here, would be happy to be corrected - but I know a lot of people like your UK/NZ case example that got surprised by changes in rules, not just Canada but elsewhere, and sometimes by airlines).
