They're saying that unless we stop our behavior in the next X years then it will be too late. We will have added so much to the system that it will "run away". This will eventually lead to the environment being inhospitable to our ways of life. Most dates ive read are 2075 or so. That's not 5 years.
They are not saying that life will end in 5 years.
This is a purposeful misinterpretation so that the reader doesn't have to listen. It allows the reader to scoff and go about their excess.
This interpretation was pushed, very purposefully, to accomplish apathy and complacency in the general public.
But back on tbe point, nobody really ever said "humanity is OVER in 5 years if we don't stop". What has consistently been said is "we are changing our environment and it will eventually change in ways that won't support our life" with various dates, usually 50+ years, given.