Here's the quote:

they are never useful or informative.

He/She seems to be referring to advertisments in general, making the statement all the more ridiculous. Advertisements are one component of marketing, and without them, all the other--more dishonest--components have all the more power. Most prominently, advertising allows the smallest companies to compete for attention along with massive companies, if only in a targeted way.

identifying ads is relatively easy technically

Oh, you think so? Well, when adblockers become standard issue, I can assure you that advertisements will be very difficult to identify, because they will be incorporated into search results, as in the old days.