Most of the time, most journalists do not know what they are talking about
Hmm. Nick Davies is a journalist and a master of the hyperbolic, non-attributed assertion.
The 'jack of all trades, master of none,' has always been a requirement for a general news reporter. On the other hand, most specialist journalists know a lot more than the general public on the subjects about which they write. Nearly all science writers will have at least a science degree, arts writers tend to have a background in the arts...and by the very nature of the trade all specialist writers are exposed to the current thinking in their particular area to a far higher degree than Joe public.
From what I've read of Davies' book (and I haven't read it in its entirety) he has a few valid points to make, but is very wide of the mark on others. Certainly, unless journalism has undergone a seismic change in the past eight years, he doesn't describe any newsroom I've ever worked in or run.