>I just wonder if humanity’s adventurous nature is leading us away from a proper focus on the sustainability of our civilization, our specie, and our fragile planetary environment?
But we still need spaceflight at least for planetary defense against asteroids, mining asteroids(so we don't have to mine Earth), etc.
Humans, simply by existing on Earth, have a huge and often negative impact on the environment. If we could somehow shift the human population off Earth, either by terraforming planets (like Mars) or creating artificial space habitats, it would have a huge positive impact on Earth's environment. We don't currently have the technology to do so - we would need space elevators to feasibly move humanity off Earth - but that doesn't mean we should move our attention away from space in the meantime.