For a planet that’s completely incapable of sustaining life?
Do you realize that it’ll take many, many orders of magnitude more resources, time, and effort to make literally any other celestial body within several years of space flight of us capable of sustaining life than it will be to fix the habitable planet we have right here?
We’re not getting off this rock without stabilizing it enough to sustain us long-term first. And by then, we won’t need to leave. Either way, though, evacuating isn’t a viable solution.
And if you don’t believe me, go talk to some biologists.