Two related articles I read this year: [1] is an account of a deeper analysis of this problem, [2] is AirBnB's experience with cutting off spending on online advertising during the pandemic. The conclusion is the same, but what is important is the analysis of the reasons for continuing ad funding in orgs which has more to do with the marketing executive's psychology and need for feeling important than any objective analysis of the effectiveness of the campaigns.
[1] https://thecorrespondent.com/100/the-new-dot-com-bubble-is-h...
[2] https://www.theinformation.com/articles/airbnbs-new-strategy...