Nonsense. Now we prepare for this to happen - by preemptively allocating places for displaced people can go. We do our best to limit how many countries are affected.
There's never a point where all we can do is throw up our hands and do nothing. There's always something to be done, even if it's not directly related to the cause of the crisis.
It said "some nations", mostly small island ones, like Tuvalu and Fiji.
That's not worldwide doom. It's just a very clear indicator of the damage that happens elsewhere, where low-lying cities like Amsterdam, New York, and much of Bangladesh have to either go elsewhere or take very expensive damage control measures.
We're at a point where it's still cheaper to prevent that at the climate level. It just grows more expensive by the day. Things can cost a lot of lives and dollars without being apocalyptic, and still worth dealing with sooner rather than later.
While some ill effects can most likely no longer be prevented, even worse things happen at higher temperatures. Every tenth of a degree makes things worse.
I like to think of it like this - some places are doomed to extreme drought and flodding and others will be mostly spared - but the environmental effects are just one piece of the puzzle, other areas of the earth will need to cope with the refugee crisis we're going to see from parts of the world becoming less habitable.
As these crises put more stress on the rest of the world we're just going to accelerate exploitation to support more people with less stuff - we're essentially burning through the world's buffer of habitability to eek out a bit more profits today.
