Earlier quoted context omitted.
I'm pointing out that even in a profitless world, a dependency ratio of 2:1 is not workable. It literally does not matter how you distribute resources.
Sure, at a certain point, not replacing enough people means the species goes extinct over time. That doesn't mean humanity going down to (random number) 1B people via gradual birthrate declines is automatically (nor rapidly ) going to lead to that, if we have enough automation to handle it, and if we have a plan to stop the process at some point.
In other words, there is a point, quite likely less dramatic than 2:1 where "allowing" people to be unemployed becomes economically absurd.