Comment by Gustomaximus

Effectiveness can vary a bunch but the majority of the time bad results are correlated to the setup quality.

There are definitely industries and situations where ads are difficult to make perform, things like a single business working against aggregator heavy environment or markets where growth is more important than profit, but overall there's reason for hundreds billions spent on online ads, this when most business can track ROI results.

One of the bigger issues I see is even 'experts' hand over control to the ad platforms to optimise their spend. For better results often you need to manipulate the systems to work in your favour, which platforms try to limit but you do what you can.

One change I feel we need is for regulation around controls and data on ad platforms to stop this ever increasing 'give us your money and trust us' type behaviour.