There were other differences. In those days, they were colonizing places where they could easily adapt their existing ways of life. Their technological base was small enough that the colonies could become relatively self-sufficient quickly.
None of that would apply to a colony on the Moon: surviving there would require advanced technology, and we don't know if it's even possible for humans to survive in such low gravity for an extended period. A colony would probably remain dependent on Earth to supply manufactured products, such as semiconductors. Modern society uses a vast range of products. It probably wouldn't be much more self-sufficient than the ISS, and it wouldn't survive if Earth lost interest in supporting it.
Compared to the moon, it was stupendously easy. There was air to breathe, water to drink, and plants to eat, and reasonably safe levels of radiation. So easy even a caveman could do it.
The only thing the moon has going for it is the apparent absence of microorganisms that cause human disease.
although i hate it, yeah.
there are plenty of places humans don't live _on earth_. Deserts and tundra are obvious. but like 70% of the surface is water, and basically 0% of the population lives there.
Maybe we need to go down before we go up. Maybe we need to survive at a few meters below sea level before we can handle living at a few kilometers above it.
Yes, I think even building a completely self-sufficient city in a desert on Earth, with the ability to build its own equipment including computers may be beyond us at this point. Obviously it would be a lot easier than doing it on the Moon or Mars, but too much of the technology that would be needed is locked up in trade secrets.
There's plenty of 3D space available at the surface of the Earth; it's not exploited either because it's not profitable or because government rules prevent it. Who wants to live in a desert in the middle of nowhere? But they want to live on Mars? It would get old fast, especially with such a laggy Internet connection.
I've read about some of the early British colonies in Australia, and doesn't seem to have taken long before they were laying out farms, making bricks and quarrying stone blocks, constructing solid buildings, setting up blacksmiths, newspapers, etc. But by then it was getting into the 19th century.
And the early colonies were plenty underplanned and disastrous.
Also, that's what my second paragraph is about. Given our current resources and capability, an experimental colony is a fool's errand.