Consider a disease like rabies. Right now there's a near-zero chance of survival to those who contract it. Let's say we discover a new mosquito variant which can spread rabies, whose population is multiplying exponentially.
Typically we might expect a disease which becomes pandemic to be survivable for some significant percentage of the population. Whereas here we might say that, regardless of how many resources we throw at rabies treatments, there may continue to be a near-zero chance of survival (because rabies had been remarkably untreatable so far).
It's a suggestion that perhaps we should temper optimism.
Note that even in the above example, a proper response might be to address the mosquito population or to begin initiatives to vaccinate as many people as possible against rabies. Likely a combination of both.
Of course it might be good to continue researching possible treatments for rabies as well, but there are other things which can be done to mitigate the impact.
I don't think climate change will be the only reason for societal collapse, if it happens. I think late-stage capitalism (which is also implicated in driving this climate change) is at least another significant factor.
I also don't pretend do know what societal collapse might look like, and what might come after. Societies don't seem to be immortal[1], and collapse has historically been inevitable. An immortal society is as unprecedented as human immortality, which isn't to say that either are strictly impossible, but that we should analyze both against historical data on statistics and symptoms which might indicate proximity to end of life.
Personally I believe the societal stressors which appear over the next few decades are significant enough that they represent a much larger chance of societal collapse than people seem to recognize. I guess we'll see.
Typically we might expect a disease which becomes pandemic to be survivable for some significant percentage of the population. Whereas here we might say that, regardless of how many resources we throw at rabies treatments, there may continue to be a near-zero chance of survival (because rabies had been remarkably untreatable so far).
It's a suggestion that perhaps we should temper optimism.