It's impossible to pick a single quote from this incredible letter from Bill Bernbach written in 1947. For those who don't know their Mad Men, Bernbach was Chairman of DDB and responsible for Volkswagen's Think Small . We Try Harder for Avis and It's so simple for Polaroid.
Every sentence in the letter deserves its own post. So you're just going to have to read the whole damn lot yourself... that is, if you're interested enough and your attention span hasn't yet been completely denuded by social media.
Here's a few topic headings:
Big agencies lose their creativity
Advertising is an art, not a science
Advertising is becoming a rational, scientific technique
Which leads to sameness / banality
And plenty more besides...
Here's the Letter:
See the full article here from MM&M.