No, it isn’t, it’s being realistic. Human beings aren’t going extinct because of climate change, nuclear weapons, or anything else. Some people would survive and they would inevitably repopulate.
I think the unbounded optimism / arrogance is that life as is will continue indefinitely, or just get better and better.
That might happen, but climate change is one of very few things that will stop it (others being nuclear war, asteroid strikes, volcanic eruptions, solar flares and other disease)