but…there’s no more planets. None that any attempt to colonize the same effort would give you vast, super vast, living space in terms of habitats compared to a planet.

If we think about whats already been done keeping them stable ceases to be seen as undo-able. Many small aquatic sealed habitats that fit on desktops exist with plants and animals in the same habitat.

https://en.wikipedia.org/wiki/Ecosphere_%28aquarium%29

https://www.dailymail.co.uk/sciencetech/article-2267504/The-sealed-bottle-garden-thriving-40-years-fresh-air-water.html

Aquariums can be mostly self contained. Large aquariums often fluctuate at first wildly but at some point they seem to “pop”, the used frequently to describe it, and they keep their equilibrium very easily. I suspect if we want build habitats we’ll need a lot of water as a buffer. Lots of soil with plants actively exchanging gasses with the soil and the biota that lives in it.

I suspect that buckhead is right if we had a cheap faster than light we would just settle on planets. I suspect that doesn’t exist because any civilization that has this would go around killing off all the others before they could compete and we’re still here.

Say, inhabitable planets are relatively rare and scattered around. They’d be used if reachable and probably hold the bulk of settlers/colonists. But then we’d maybe have habitats with civilians at transit nodes, trade points.

All that would actually depend pretty heavily on the actual mechanics of interstellar travel, too.

The other consideration would be the definition of habitable. I’m just casually assuming that an alien biosphere would have no biologicals that were evolved to harm us at the microbial level, but it could have chemical environmental factors that would not be obvious enough to cause us to declare “uninhabitable” right away but might sneak up on us. We might have impressive analysis capabilities, but it’d still be an alien world.

But the planetary chauvinism isn’t crazy. If we developed an FTL drive that allowed us to get to other stars in a modestly timely fashion and habitable worlds are common I don’t doubt that we’d remain a planet-bound species. Except for special needs (military bases, shipyards, mining perhaps), we wouldn’t bother laboriously creating vast habitats in space when we can just plop down on a virgin world and just start living there.

We prefer the term “Humanists”…