[teh_g]

TIL about Georgists, thanks.

Regarding whether it's "pretty limited", yes and no, imo:

Yes, compared to, say, the size of a continent, the amount of new land is tiny.

However, new land is usually made in highly sought-after (high-density, high-value etc) areas [citation needed]. So it would make better sense to compare the surface of the new land to the surface of the adjacent area.

For example, the polders in the Netherlands significantly augment the country's surface. The artificial islands in Tokyo Bay significantly add to the real estate of the harbour. The artificial islands in Dubai and Bahrain significantly add to the coastline.

I think that this is enough for OP's analogy between domain parking and land speculation to reasonably stand.