It’s not in any way a relevant comparison.

The Black Death was a sudden decline.

This will be a slow motion demographic move through a series of unusual states of population mix as the various cadres go through the stages of their lives.

Your answers are solving some of the wrong problems.

When everyone knows there will be less consumers next year and even less in a decade and so forth what is the incentive for future investment? Using the current assumptions means the whole system collapses. So the assumptions must change. No amount of focusing on robots and that side of things will address these issues.

Will the robots change things as you suggest and do we need to work on preparing for that? Yes. Plenty of interesting thought work to do as you suggest.

Is that enough to deal with a downward demand curve being the norm for centuries? No.