> the force-multiplier effect of writing meant that we benefited more from the new skills that appeared over the next 50 years than we lost by no longer developing the skills that writing made irrelevant.

Not to mention the increase in the number of people able to participate in the activities. While being able to orate Homer's epics from memory is useful, I think it is far better that everyone has the ability for their parents to share the stories with them from a book than having to wait for the traveling orator to come around (never mind having to sync up with the flashbacks to make sure everyone is up to speed). We've seen it before too: stage theater to movies; concerts to vinyl; TV and movie theaters to VHS; physical medium to the Internet.