You're still coming at it from a small-minded approach and defeatist attitude. The facts are simple, stay on this planet and we are extinct no matter what. We have to overcome the issue somehow to survive
No, I have explained I have believed that humanity can and should expand out in to the universe since I was very young.
But as you mature, and learn more (and really learn that you actually know very little about anything), and data changes and begins to more strongly support specific trends, you realise that there are bigger, more existential problems to solve first.
There is nothing simple-minded and defeatist about facing reality. In fact, maintaining that the only way to “save humanity“ is to leave Earth is simple-minded and defeatist. Especially given even in the best case scenario very few people will actually ever get to leave earth, which means that strategy condemns must people to suffering and premature death on a dying world (for human habitation, that is).
It is not only simple-minded and defeatist, it is cruel and selfish.
And, even if a small number of humans do somehow escape Earth before climate change degrades our capacity for space travel to zero, it also ultimately sets up just another cycle of colonise > exploit > degrade > disaster > escape > repeat.
Nothing is truly solved without confronting what we have done here and mitigating the harm we have caused, both for the sake of the billions that will never leave earth and future humans that might (as well as the extraterrestrial ecosystems we may one day call home).
Beyond all of that, developing the capacity for mass human migration to other planets will take substantial amounts of time, energy (literally), resources, unprecedented levels of collaboration, and truly mind-boggling amounts of capital. None of that is going to be available in a world being ravaged by climate change, where most groups of people are in conflict with every other groups to hold the resources necessary to merely survive.
If you want to leave Earth, you have to first work to prevent cataclysm here.