Speaking as a PhD, I can assure you that just because PhDs research ways to make a thing work does not mean it does. Nor are they, or those hiring them, immune to presenting their results in the most optimistic possible way.

I am personally acquainted with several active fields that have been trying to make things work for 20+ years with very moderate success. They present their results which amount to "barely better than nothing" in order to keep funded. They also make the same arguments you do, "it stands to reason that it should work", to keep the money flowing.

There is the drug industry, which is chock full of new drugs that are barely better than placebo or generics, if they are at all. The results are hyped because it keeps the cash flowing. It would not be entirely true, but nor would it be too far off the mark, to say that almost the entire drug industry is based on fraud and exaggeration. And that industry is far more transparent WRT data and superficially altruistic than the advertising industry. This example is perfectly parallel because no one denies advertising works, just like no one denies antibiotics work, but the difference between new and old drugs, just like new and old advertising methods, seems to be greatly exaggerated.

Google built its entire empire based on contextual advertising, not behavioral targeting. With Facebook you may have an argument, but Facebook has a very special dataset not available anywhere else, and I would also add that Facebook makes the same amount of money whether behavioral targeting really works, or if they've just convinced their advertisers that it does.

I am neutral on the subject of whether it works because I have never looked into it, but "lots of self-interested people say that it does" is not convincing, and the fact that such an argument is so frequently made makes me think there is no actual proof.