You make some very interesting points. I won't deny the power of modern media to convey information and understanding. My main point is that we should not assume that such media provide an adequate replacement for written information which, among other things, can provide compact, durable, portable, and (in book form with a proper index) rapid access to informational detail.

Both ways of conveying information can co-exist, each used for its relative advantages.

And maybe our technologies are evolving to an extent that they can ultimately provide many of the advantages of written language without people having to learn spelling and grammatical structure. Will we ultimately be able to get all of our detailed information just by speaking to Google or Siri? ("How many teaspoons of ground cumin and coriander should I use when I make the most popular recipe for vegetarian chili?")