I'd love to see some research about this from an unbiased source showing that targeted advertising produces great results in small businesses (<100 employees, or <5M revenue yearly).
It would also be important to know, not if ads can produce great results, but how many companies do they provide great results for? Even better, what percentage of all business that run online ads get a positive return on their investment, and what is the average of that return.
My personal experience is that it is pretty hard to get consistently good performance running campaigns on FB or Google. It requires a lot of learning and a lot of trial and error. On top of that, they constantly push you to spend more by giving you dubious recommendations on how to “improve” your campaigns. Very hard to believe that the average small business is actually capable of running good campaigns and consistently make money from them.
What about all the actual small businesses that have positive ROAS? There are millions of them on Facebook's platform. What kind of other research are you looking for?