>If that's your view, the first priority of every single person should be to work towards stabilising the climate and reduce our impact on the enviromnent

But why though? If that's what you believe and there's nothing more, we know the sun is going to explode and destroy everything and an asteroid impact is likely to happen that destroys even sooner than that, so why does that matter?

Because we could cook the planet in a matter of decades or centuries rather than waiting ~5 billion years for the sun to explode, which would give us plenty of time to figure out how to explore space sustainably rather than some kind of delusional Musk-like sci-fi fantasy of bases on Mars in the next decade.