The poster said ‘a mass extinction’ which does not mean what you seem to think it does: “An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth.” https://en.m.wikipedia.org/wiki/Extinction_event

It seems very fair - even overly cautious! - to push the inevitability of that out to 2100 when many would say it is already in progress.