How would we get a significant number of people to this planet? We would need to apply and quickly adapt the most cutting edge technology to survive - would we only take scientists, engineers and mathematicians? How would we successfully synthesize soil quickly enough? How would be know what kind of weather patterns to expect and how would we cope with them? Category 5 hurricanes could be a daily occurrence. Would we get enough sunlight? How would we make sure the temperatures do not exceed tolerable limits?
Why not stay here on earth and gradually reduce the human population to around 500 million people. 500 million people could maintain a high standard of living without making Earth uninhabitable. We could allow large areas such as South America to go back to being forests and live in those areas that are most conducive for human life. And we could use space technology to mine asteroids to provide additional raw materials. We could even start removing excess carbon dioxide from the atmosphere and eventually bring it down to historic levels. 500 million people are few enough that we could all eat a lot of meat and it still would be sustainable.
And we need a conversation about who does and does not care. The Middle East does not care about the planet. Neither does India or China or Indonesia or most of Africa. India's population has almost caught up with China. Regardless of reducing the world population or escaping the planet, how would we do this if most of the planet is not on board?