Hurr durr, there was a massive impact 60 million years ago, 11 deep into the human evolutionary chain when our great ancestor looked like a rat (carpolestes), and 75% of species went extinct you think the planet wont recover.
Oh yes, it will, it will recover. And life will likely flourish. Without us.
So we are on the cusp of feasibly colonizing other worlds but the idea of colonizing our own world as it becomes less and less habitable over time with the same technology is somehow entirely alien to you.
We're on the cusp of being able to ship huge amounts of materiel to Mars to support a small colony.
We're not really on the cusp of being able to run a fully self-supporting colony. We're pretty far from being on the cusp of being able to do the same en-mass on earth.
You made the argument yourself we are already making it uninhabitable for us. And if living in a dome is okay for you then go to one and stop wasting our time. When your dome fails don't come crying.