> The proposal is to make it economically unviable to do socially suboptimal things with common resources.
Well, the resources in question aren't "common resources", they're economically rival resources that already belong to other people.
So the argument is to artificially constrain people from using their own particular resources to do "socially suboptimal" things, but in this case what's being posited as "socially suboptimal" is actually just a normative "ought" opinion posited by a specific faction in opposition to the observable "is" manifested by society itself.
Dress it up in whatever language you like, but the underlying position remains "I want to force people to conform to my preferences at the expense of their own".
> The underlying principle is that land - including natural resources as a whole - is finite. It's a common good owned by humanity as a whole;
That's a very poor principle. Every question in economics and political philosophy deals with the complex interactions of different subsets of "humanity as a whole", so treating humanity as a whole as a singular agent is outside the realm of any kind of useful analysis.
And the concept of ownership is something we apply to economically rival goods -- including and especially land -- precisely because possession and use of rival goods are inherently exclusive. Ownership must be exercised by some narrowly construed party at the exclusion of others, and all of our models of property rights serve the purpose of resolving competing claims to the same resources precisely because ownership cannot be aggregated.
The relation of high-level abstractions you're invoking here might make for a nice slogan, but "everything aggregated into a singular unit is owned by everyone aggregated into a singular unit" is completely useless as a model of reality.
> Allowing individuals to hoard those finite resources is bad for society.
Individuals, in aggregate, are society, and what's good or bad for society is entirely a function of what is good or bad for the individuals who constitute it.
When different individuals have conflicts of interest or divergences in values that bring them into dispute, we need solutions for resolving those disputes in a manner that is maximally favorable to all sides, and which assiduously respect the rights of all individuals involved. Property rights are an important example of doing exactly that.
The moment we adopt a "winner take all" model for resolving social conflict, we raise the stakes of participating in society in the first place, and and up on the road to social dissolution. As high minded as the abstractions you're invoking seem to be on the surface, the practical reality of your proposal is that the state will act as a universal landlord, and put control over how everyone is using their own property in the hands of whichever faction is politically dominant, absolutely leading to a "winner take all" scenario where those most skilled at politics can usurp the property rights of everyone else. It's a recipe for disaster.
> Under a land-value tax system, individuals can do whatever they want, but they're appropriately charged for their negative externalities.
We already have a system of legal liability for holding people responsible for their negative externalities, and it works very appropriately, by making people who cause negative externalities financially responsible to the specific parties who those externalities have harmed.
The approach you are proposing would be universally preemptive, rather than remediative, charging people across the board regardless of what externalities they have or have not caused. And it would put the proceeds of those charges not in the hands of the people who were harmed by the externalities, but rather in the hands of a separate organization entirely, one which may or may not have an incentive to apply those funds toward the remediation of the externality, but might have entirely unrelated purposes that it diverts those funds to.
> Market forces alone are incapable of correctly pricing deals involving common goods, because most of the people who are implicitly participating in the transaction
There are precious few genuinely common goods to which markets are applicable in the first place. Markets conduct trade in scarce and rival goods, but common goods are definitionally non-rival hoods, for which a single unit of production satisfies every disparate instance of consumption simultaneously. A classic example is military defense, where a single army deters aggression against the country as a whole, and does not produce distinct units of defense consumed individually by each resident.
We already typically rely on non-market solutions for common goods, e.g. having them provided directly by political states and funded via taxation. There are lots of problems with this, especially the principal-agent problem, and many people are trying to come up with ways to make pluralistic markets applicable to these goods by disaggregating them. But here you are proposing to take things that aren't common goods, like land, and make them subject to the same failure modalities we experience with common goods.
> In a democracy, the state is how the public as a whole imposes its collective will;
No, this is absolutely false, and is indeed an extremely dangerous idea that twists democracy into a kind of quasi-totalitarian system. Democracy is a tool for ensuring that the political state is accountable to the public generally, as a means of preventing abuses of power. It functions as a brake pedal, not as a gas pedal.
A large and pluralistic society dos not have any sort of singular "collective will" in the first place -- societies are aggregations of lots of disparate individuals, who often organize into subcultures and factions who have very different goals and interests -- and the purpose of law and politics is to mediate between them in a way that enables each to maximally pursue their own particular will within their own particular boundaries without conflicting with each other.
Democratic processes are meant to ensure that that meditative process remains honest and accountable, not to attempt to replace it with some pretended distillation of everyone's diverse values into a single set of principles -- the latter is logically impossible, and attempts to do this invariably result in a single faction imposing its values forcefully onto everyone else.
But I will note that the closest thing that resembles the "collective will" of society as a whole are the patterns that emerge from the interactions of all individuals, communities, and organizations, at all levels of scale and complexity. The behavior of the state, one particular artificial institution within the vast complexity of society, is absolutely not a reliable indicator of the nature of the whole, no matter how democratic its processes may be.