Bringing land into use is a service ie Labor.
Hope this helps.
I suppose we're all buying and selling the labor from surveyors and the register of deeds then. It is certainly convenient for some people to call this legal right to exclude all others from exploiting resources from a defined area on the surface of the ellipsoid as "owning land".
Same thing as natural resources. You are conflating two separate things.
What gives Land its economic value and meaning is its relative difference in productivity ie marginal vs inframarginal Land.
The Saudis are rich because their oil reserves are cheap to exploit relative to those found at the margin of production, like Canadian Tar Sands.
That difference isn't due to the efforts of the Saudis supplying it. It is purely natural advantage ie Land.
What is true of oil is true of all natural resources, but particularly 3D space ie Location.
Hope this helps.
It is all humans. The energy and engineering requirements of exploiting land pale before the sociopolitical requirements of exploiting it for any particular person's benefit.
A human is not a sellable slave until a slaver captures him and drags him to the block. The stolen goods are just goods that have been detached from the previous labor of legitimized title-service and security providers.
Inanimate objects have no intrinsic value. Every last speck of their value comes from human desires and expectations.
Imagine, if you will, two planetoids orbiting a star 1000 light-years away. One of them is 100 million metric tons of shiny 24K gold. One of them is 100 million metric tons of stinking manure. Which is more valuable?
While it is true that the surface area of the ellipsoid is not changing, economic resources are only counted when they can be brought to market. You don't usually create new [economic] land by dumping dredged sand into a harbor--though such projects do exist. More often, new land is brought to market by building a road to it, or an airstrip on it, or a pier on its shore.
And such land is not fungible, it most often has multiple competing uses, and some non-competing uses. And those uses can be amplified by capital improvements.
When I want "land" in a city, that's usually at least 75 m^3 of interior building volume as a safe location to sleep and store all my useful stuff. You can make more of that in the same footprint by erecting buildings with more floors--not even necessarily taller, just more floors. Or you can dig down, and again, add more floors.
And I value proximity by time, rather than distance. So you can make land "closer" to the city by enabling faster transportation. The 50th floor of a building with a fast elevator is closer to the ground than the 50th floor at the same physical height, but with a slow elevator. The suburb next to an expressway is closer than the one without convenient roads.
We really still have plenty of available land, barring situations like Hong Kong or Singapore. The Chicago-Pittsburgh megalopolis has more untapped land supply than the Boston-DC megalopolis, but those acres can all be gridded and developed to the limit of human engineering ability, which is a pretty darned distant limit.
The problem is usually that development is often politically constrained such that supply cannot change as quickly as demand. You just can't build fast enough in Silicon Valley, and you just can't demolish fast enough in Detroit.