The assertion about the usefulness of Google ads is flat out wrong. I realize it was probably meant to be hyperbole, but it doesn't come off that way.
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.