I have been enjoying reading a lot of Science Fiction lately and was especially intrigued by the “Three Body Problem” trilogy. Almost uniformly the authors that have covered this subject point out that once humanity has become divided yet again by a new axis of division. “Up Well” vs “Down Well” the same thing will ultimately result as has every other division of humanity.
It seems to me a powerful argument can be made that “getting off this planet” could actually be the mistake that ends humanity rather than saves it. In several ways, the least of which it could bring us into competition with a consciousness that would have remained unaware of our existence and would also be hostile. In truth, it would likely cause inequities that humans would use to rationalize the murderous behavior we seem to all to happily engage in as a group but abhor as individuals.
The three body problem series was an interesting read. The universe and local physics actually just being the result of whatever dimensional warfare occurred there was a pretty neat idea.
We will never get off the planet in any real way until we can plan over the course of 100+ years or prolong our lifespans so the people that care about space colonization can continue to work on it for long periods.
Freegards
Babylon 5 and others showed how that can be done by spacefaring species. Mass drivers routinely used to send cargo between satellites and ships get used to throw mass at high speeds onto planets, destroying them like multiple major meteor strikes would at low cost to the space farers.
I think the threat of this was used in “The Moon is a Harsh Mistress” to get independence from Earth.