here. I suggest that what the Changelings know is survival skills and that human life is more than survival. Of course, post-Change life has not been reduced to a continual struggle for mere survival. There are also satisfying social interactions, cultural traditions and the genuine enjoyment of the fruits of their labours. Nevertheless, what they value is knowledge of survival strategies that most of us no longer need to spend our time on because we have been freed to develop other potentialities.
Poul Anderson's Time Patrolman Manse Everard mentally lists the pros and cons and then the legacy of the Roman Empire:
a widened world
Legacy ("scattered through the wreckage")
memories of what once was
stuff to be salvaged, treasured and built with again
the memory of "...a life not given over to naked survival."
-Poul Anderson, "Star of the Sea" IN Anderson, Time Patrol (Riverdale, NY, 2006), pp. 467-640) AT p. 604.