Color me unconvinced. Google can't even figure what language I speak even though I voluntarily provide them the information in several different ways. I can't understand half the ads they serve me.

Google doesn't choose what ad to show you. Google serves up a platter of details and auctions the ad placement off to the highest bidder.

That platter of details is not shown to you, the consumer.

What you are experiencing is that your ad profile isn't valuable to most bidders, ie you don't buy stuff as much as other people do, or your ad profile is somehow super attractive to stupid companies that suck at running ads who are overpaying for bad matches.

It is not evidence that google knows nothing about you.

Google is pleased that you think they don't know you. It helps keep the pressure down when people mistake this system for "Perfectly target ads". The system is designed to make google money regardless of how good or bad their profile of you is.

It's not just the ads though. Am I to think that Youtube helpfully replacing a video title (whose original text I understand) by a half-assed translation into a language that I don't speak is actually Alphabet playing 5D chess ? If so, hats off to you, Google. I totally fell for it.