Of course in some cases it ends up like that, but as someone who sees stats for a very big company in the IT world, re-targeting does work. I see a large number of metrics including ROAS (return on ad spend), and the false negatives are more than made up for by successful sale conversions.

No - it focuses advertising efforts on people who have visited your website. So, you look at a jacket, but then aren't sure you want to buy it, retargeting makes you see that jacket again and again until you change your mind. Then you keep seeing it anyway.

retargeting is crazy effective (for me at least). After buying a home, I spent a lot of time buying things like tools etc. Often times i'd be about 90% ready to purchase something, but for some reason or another i'd decide against it. Those ads following me around would usually get me across the finish line. I ended up installing adblock.

Retargeting works, but it requires optimizing. Often this is not set up well, because it works so well without optimizing it.

It requires a high level of technical chops to see this and set up. Most traditional marketers just don't have the skills to set it up or the correct access to make the right changes.