As with almost everything in life, there are multiple factors to take into account.

We recently ran several drip campaigns, as well as a few fire-and-forget campaigns, together with corresponding ads through Google. There was a marked difference in customer uptake before and after the ads. We have also pretty regularly received feedback on our ads.

In fact, that is what we have observed over the years. Customers are conscious of what the ads say, where they get placed, and - usually - can crosscheck the quality of the ad with that of the product.

In my experience, it is rash to generalise and say that ads are not useful.