The problem is that in high demand areas, it can be profitable for people to buy property purely as speculation without ever having people live there.

As I pointed out earlier, this problem is solved by adding building supply to balance out the supply-demand imbalance causing property to appreciate and be a source of speculation. No one will "invest" in real estate if adequate supply causes no price increases. Any ad-hoc state involved bandaids like rent-control, foreign ownership laws, etc. are unnecessary.

Land and Real Estate has other aspects of the demand aside from just "a roof over your head" though. Location and other factors play into it in a big way. For instance if you have a parcel of undeveloped land at a lakeshore, the supply isn't "all land available in the region", it's "All land along that lakeshore" which is a much smaller supply. And lakes are generally a desirable place to live, so the demand is likely high.

It doesn't really matter that there are exceptions where some areas are naturally more desirable because land isn't fungible. What matters is that there are available housing units approaching the limit of construction cost pricing so that people can have a place to live without being affected by luxuries like "wanting a lakefront home."

My point isn't that there aren't some exceptions it's that there are tons, maybe literally hundreds or thousands of factors into the supply/demand equation here.

what kind of internet is available in the area? How close are you to grocery stores? Is there a HOA that you have to pay dues to? What's the weather like? Is the home up to date or is the wiring and plumbing likely to need a lot of work? How big is the lot? How walkable is the neighbourhood? Is it near a smelly dump? What's the crime rate like? What are the schools in the area like, how close are they? How much access is there to transit?

It's not as simple as just "Build more housing" society also has to adequately service the people who want to live in that housing. If our lower income housing is all just bare minimum roof over your head and no access to anything then no one will want to live there, which also means that supply will not affect the demand on housing that has better access to amenities.

Internet infrastructure, closeness to grocery stores, homes being up to date, walk-ability, close schools, access to transit, are all improved by building more dense housing.

We can also be quite certain that providing the bare minimum housing pulls in demand from those more luxurious options (wants) to the more economically practical option (needs), because the bare minimum option was never available. We'd be giving people more choices and at least some would take it.

Then if you have so many people that "demand" a certain standard of luxury housing, then they will have to compete and pay the premiums for the actual limited resources like lakefront property or great schools (living near other like-minded wealthier people). That's the realities of scarce resources, and is fine, since there's not much we can improve there. But the major gap is providing the bare minimum of housing which we are currently not doing.

How do you add building supply when there is no undeveloped land? There are no empty lots in high demand areas.

You'd have to increase density, and most places it will be difficult to displace people from their homes to tear them down and redevelop them.

Make other areas more attractive?