He actually talks about this in his book, democracy already existed before newspapers became big (or even existed). People got informed through books, pamphlets, essays, debates and public gatherings. Now, some articles do inform the people more, one of the big examples is Watergate. But the difference in quality and research between the Watergate articles and the daily news is immense. Most political news-articles are nothing more than copy-pastes from what a politician sends to the writer and newspapers aren't the only medium where investigative journalism can exist. In my home-country a one-man journalist published some big scandals on his blog which showcased some unsavory corruption in one of our cities, all the big newspapers could only report what he already said, they had zero investigation themselves.

The other part is, do daily newspapers really inform you? Do they follow up the promises of candidates? Do they analyze effects of laws? Do they give you a neutral view of the situation?

Democracy can work fine without newspapers, maybe even better. Politicians in my country focus mostly to solve small fires without addressing the problems underneath it as those get them in the news but the big problems with complex solutions don't give them the same return of visibility in the papers versus the work required to fix it.