This is patently false. I have friends who have worked years developing solutions for doing ad effectiveness comparisons. They are A/B tests in most cases but

This is patently false. I have friends who have worked years developing solutions for doing ad effectiveness comparisons. They are A/B tests in most cases but some methodologies require a lot of sophistication because of problems tracking conversions. Traditional ad platforms like TV, newspapers might not have done this but online ones surely do. Infact that is one point they consider an advantage as you can measure effectiveness unlike the traditional platforms.