The Earth has more land than mankind will ever need. The Earth has effectively infinite energy from the Sun. And most of the resources we need are derived from biological matter, which Space lacks.
People don't realize how rapidly fertility affects populations. Take a place with a fertility rate of 1. That means each successive generation (which tends to be about 20 years, or the the window of fertility for a gen - from age ~20 to ~40) will decrease in size by half, in a compounding fashion. So over 1 century, that's a 97% decline (0.5^5) in generational size. Extinction comes shockingly fast.
But the opposite is also true. So what's going to happen is that low fertility populations are simply going to go extinct. That's going to be just lovely for humanity as it also corresponds with higher income, higher education, higher liberalism, higher secularism, and so on. And the current high fertility groups will come to quickly dominate the world. So it's kind of amusing in a way that Biblical texts will indeed come to pass - you'll have groups like Amish or Haredi, the meek - who happen to have high fertility rates, indeed inheriting the Earth.
This is part of the reason fertility is, by far, the biggest crisis facing humanity today. All love to the Amish and Haredi, but I don't want the Earth to turn into a planet of overalls and sidelocks. Even that would probably be just liminal, but we need some sort of high tech, high intelligence, high fertility sect to emerge. It's probably going to require something to akin to a modern religion, though presumably without a deity. Or maybe the Mormons had it right all along.
So, SpaceX?
I get it though. This is just how naturalism looks like when runs out of arguments in its favor.
"The Earth has more land than mankind will ever need."
"The Earth has effectively infinite energy from the Sun.
I see no exaggeration, obvious or otherwise. Scientific consensus is that mankind's population is going to peak in the next century.
> mankind already needs more land than Earth has
By what basis? There's no shortage of land. There's a shortage of land close to popular population centers, and that tends to be the land that people want to live on most. But that's an inherent geometric and social problem which outer space definitely doesn't solve, in fact it makes it worse.
> more energy than Earth can spare
Earth doesn't provide energy, the sun does. Even fossil fuels, biomass and wind power were all originally energy from the sun. The exception is nuclear - Earth does have an unusually high concentration of heavily elements like uranium and plutonium.
The bottleneck has always been development and delivery, not availability of energy itself. On just the land the US currently uses to grow corn for ethanol gasoline, we could build enough solar panels to power the entire US. And I certainly don't need to tell you about nuclear - the only reason entire civilizations aren't already powered by it is the time and expense and risk of building the plants.
What energy does outer space provide? You have solar, which we have here, and nuclear, which we have here. (You also have a variety of ideas that exist in science fiction but not the real world, like dyson spheres - I surely hope you aren't referring to such as the basis of your arguments.) None of this is new, and none of this solves the problems of development and delivery, in fact it makes both problems significantly worse.