[davidivadavid]

Except that of the books published 100 years ago, the ones that stood the test of time and are still published today are far more likely to be of high quality by today's standard, while most books published in any given year will inevitably be forgotten.

Did editors exist 100 years ago? Erm, yes they did? According to Merriam Webster, the term was used in its current acception in 1649. And the job done by editors could arguably have existed for a much longer time.