I don't think it's pessimistic at all. The Earth is fucked. Not by humans, just by itself. It will be fucked within a few hundred million years simply because

I don't think it's pessimistic at all. The Earth is fucked. Not by humans, just by itself. It will be fucked within a few hundred million years simply because the sun is going to get bright enough to boil away the oceans. If we want any hope of our legacy to carry on in the universe, we need to begin exploring the possibilities now, because we have the scientific knowledge and technological capabilities to begin that exploration process.