This is really, really not true. Advertising lift has been well studied, especially in metastudies spanning hundreds of digital campaigns across Facebook and Google. These are independent academic metastudies, with hundreds of millions of impression data samples.

Positive lift in the range of 0-20% is very common, and many statistical aspects of causal inference on ad impacts are well understood.

Negative lift and flat campaigns are real phenomena too, and it does deserve more widespread publicity that negative lift happens in an appreciable number of campaigns, but that doesn’t take away from the overwhelming evidence that digital advertising works and that the mechanics of positive lift are well studied.

Here are two of the foundational papers in this area:

- https://www.kellogg.northwestern.edu/faculty/gordon_b/files/...

- https://www8.gsb.columbia.edu/media/sites/media/files/Garret...

Particularly Figure 1 (page 26) in the second link. That figure alone utterly refutes any nonsense claim that digital advertising doesn’t have provably positive ROI.