I’ve paid close attention over the past few years and have found >80% of the retargeted ads are for something I just purchased (and they are usually the “single purchase” type product, similar to the fridge analogy you used)

Even if a big share of your ad impressions falsely target someone who already bought (see sibling comment) the remaining impressions lead to an increase in conversions at a comparatively low cost per conversion.

As you said, this will vary from business to business, but I have seen very successful retargeting campaigns in b2c e-commerce as well as b2b lead generation.