High-speed rail (300+ km/h across the prairies!), buses, even air travel are mass transit options that would work as well or better than personal cars for addressing the vast majority of travel across Canada.
Buses are a thing of the past in Canada, they're far too slow and the countryside is too spread out to make feasible routes. They also used to cost almost as much as a plane ticket and take 10x the time. When intercity lines outside dense population centers DID exist they were pretty much empty all the time, hence their extinction.
High speed rail could only serve major centers across the country. Other than the Toronto to Montreal corridor, population centers along the rail lines are too far apart. For example the distance between Toronto Ontario and Kenora Ontario is roughly 1500+km, so a high speed rail trip would still take 6-8 hours between them at best. The train would be mostly empty too because there's just not a lot of people going between non-major cities. It's not like just because a rail line appears between places people are going to start going between those places all that much more. There's just no way the operation costs for high speed rail would be covered by fares from a handful of people.
Air transportation is only good for longer trips between two major centers in Canada. If you're going to/from smaller regional centers for most of Canada the commercial airports don't even exist, and if they do the flights are infrequent and the costs to fly in/out of them are absurd and the flights might even take far longer than just driving. For example to fly between Kelowna BC and Kamloops BC, a 150km drive, costs $300-$500+ for the ticket and takes about 5 hours (not including travel to/from the airport, check-in time + waiting at the gate + waiting for luggage) due to a stop in distant Vancouver. It's just not feasible to airlines to have short direct routes, so they don't. But again you're not going to find airports with commercial flights for about 90% of the towns in the country because the towns are small and don't have airports (except if they don't have roads to connect them like in the north).
To summarize, unless you don't go anywhere or you're only going between Toronto-Ottawa-Montreal by train or flying between distant cities or in a remote village, you're likely going to want to use a car otherwise the alternatives can be absurd.
Connecting just the majoriest of cities, the Vancouver, Calgary, Edmonton, Regina, Saskatoon, Winnipeg, Toronto/Hamilton, Ottawa, Montreal, Quebec, and Halifax metro areas would cover, by some quick math, over half the country's population already. You'd get a good chunk more if you add in the rest of the Golden Horseshoe - Waterloo/Kitchener, London, Windsor, Kingston - and a few other major regional centres (your Sudburys or what have you) to break up the trip.
A hub-and-spoke model - with high-speed rail connecting those major centres, conventional rail connecting those to smaller - but still regionally significant - large cities like Kelowna and Kamloops, and then buses from there to further flung places would easily cover a more-than-sizable majority of the country's travel needs.
On the one hand - part of the reason for poor ridership - and thus poor cost efficiency - of buses and trains is a consequence of a 20th century planning mindset that prioritized car infrastructure. And it was a vicious cycle. Service was infrequent and slow, so people preferred cars; people preferred cars, so more infrastructure was built for cars; fewer people road the trains or buses, so economies of scale got worse, service was made even more infrequent and funded even less...so more people buy cars. More people will ride trains and take buses if they run more frequent and are faster, especially as the cost of operating a personal vehicle has gone up. If you build it they'll come and all.
But on the other hand, to me much of your cost analysis is moot. Trains and buses won't make much money in ticket sales - well, so what? How much do roads for cars make in "ticket sales"? The governments have happily funded car-related infrastructure for decades despite the fact that they don't, directly, get a penny back from it. Why do rail and bus have to play by different rules?
To your other point, the hub and spoke trigonometry doesn't apply to Canada, the population's not laid out in that way. It's already for the most part a linear layout produced by a set of parallel competing rail lines running a couple hundred km from the US border. The rail was the factor that made the majority of the country's settlements. In America or other countries I think your point is absolutely fair though, because there's actually vertical girth to the nation that makes an actual hub and spoke system feasible.
Ultimately though I just don't believe anyone would use a train to spend 15-20 hours to get from Toronto to Calgary on high speed rail. Or even 4-6 hours to get from Vancouver to Calgary (likely not possible anyway considering the terrain). They're going to fly.
And almost no one is going to take a train from Regina to Winnipeg when they absolutely need a car at their destination to do anything anyway. Even the proposition of connecting Calgary to Edmonton is massively ridiculed because people understand how exceptionally light-weight your trip must be to forgo a vehicle at either end for the sake of saving maybe an hour by taking a train. It just seems silly considering the realities.
Actually, I'm curious - I don't know a lot about China (although I know that they're maybe not the ideal comparison for Canada for any number of reasons). What should I read? Wikipedia says...
The improved mobility and interconnectivity created by these new high-speed rail lines has generated a whole new high-speed commuter market around some urban areas. Commutes via high-speed rail to and from surrounding Hebei and Tianjin into Beijing have become increasingly common, likewise are between the cities surrounding Shanghai, Shenzhen and Guangzhou.[144][145][146]
Also bonus of developing secondary cities along routes, which is actually perfect for Quebec-Windsor corridor that contains half Canadian population along 1200km line. It's almost a no brainer if Canada wants to keep immigration flowing and decongest new comers settling in a few cities. Extra bonus it's electrified, Canada can build trains, and it's more comfy than aviation.
Primary problem is Canada/US can't build large scale infra anymore, especially not proper HSR that needs to be elevated, more so to have it route/link to networks that connect urban centres.