The thrust of it is that the federal government would withhold funding to municipalities unless they meet certain home-building targets.
Critics worry that this will accelerate suburban sprawl in order to meet quotas. There are some provisions regarding rental housing and transit infrastructure, but with unrealistic time/budgeting constraints.
To be fair, yes, Canada has the second-largest land mass on the planet. ~90% or more of that landmass is largely inhospitable for larger communities though, whether it’s the Canadian Shield and the fact we can’t grow any crops on that or dig through tough rocks, the Tundra and Arctic (where it is way too cold to grow anything, much less settle), vast distances of forests - it is a lot tougher to build infrastructure in most of Canada, leaving it pretty much to the places already with larger population sizes. And even then, most people are still choosing to go to the three cities and immediate outlying areas where the most economic influence and possible social connections are - Vancouver, Toronto, Montreal.
It would seem deceiving, given how large Canada is, but there are very few places outside of those major metro centres where people want to live, or can even live comfortable lives and be productive. Honestly, given how little good land is available in Canada, it would make far more sense to cut down on suburban developments and focus on higher-density, transit-minded communities. Single-family homes are way too inefficient for what we actually need, and having politicians and citizens who demonize quadplexes and other high density options do not help at all.
This is the real issue. Having grown up in a dot on the map in the middle of the Ontario boreal forest on the arctic watershed side of the Shield, I can tell you that it isn’t all that much harder to build infrastructure there than it is further south (sometimes takes a little longer because of longer winters, that’s all). It isn’t even horrible land agriculturally as long as you take the shorter growing season into account when you’re choosing what to plant. So more of the land is usable than you might think. However, people want to go to the places where people already are.
Even if you take only 10% of Canada’s land area, that still exceeds the land area of 160 other countries in the world, including many with far larger populations such as Pakistan (6x the population of Canada with less than 9% of the area). By the way, Pakistan is a highly mountainous country with more than half of its area covered by uninhabitable mountain ranges and deserts.
You didn’t address my points about investing at all. I think there’s a pretty good case to be made that governments are fighting against the construction of new subdivisions in order to protect the property values of existing single family homes. It’s not about stigma, it’s about the fact that too much of the upper middle class’s wealth is tied up in real estate and the government is terrified of jeopardizing that!