One should not take this quote seriously. Doyle was not hoping his Holmes should be a model for anyone to follow. He is some kind of anti-humanist. I see Holmes stories as some kind of exercice de style, and in real life the reasoning part of a detective work is anecdotal, I believe the real good detective is the one who can put himself in the brain of his prey, see Maigret for example.

TLDR: BS! Reading good books unrelated to your main work is more necessary than ever. And that'a why closing the pipes of the noise is a good idea.