Also, the climate doesn’t even have to become worse for climate change to be a problem (although it will, and rising sea water levels bring their own problems).

Also, the climate doesn’t even have to become worse for climate change to be a problem (although it will, and rising sea water levels bring their own problems). The mere change in weather patterns means that assumptions underlying human civilizations for millennia are not true anymore. You will (we already are) see vast migrations with people resisting the migrators leading to more war and strife. Cities built on the assumption of the presence of clean water will no longer have that clean water anymore leading to the destruction of the city, it’s economy and the lives of the people in it. The rapid change in climate is a huge problem even if theoretically the climate was somehow becoming more suitable for humans.