It seems like you might be missing part of this discussion: with widespread environmental collapse as described -- irreversible decline -- humanity faces extinction, regardless of the number of jobs in the economy.
Yes, but unrealistic measures won't motivate people to make the necessary changes. There are costs people will pay and ones they won't. You're not going to care much about the future if your kids go hungry now because there are no jobs. Particularly when it's based on a future prediction that might turn out differently.