The excuse for these kind of ads is that it's just machines making correlations, but I've always thought it's mostly easy to solve: they should only show you ads for things you bought when it's the kind of product that other people have bought more than one of. So, that would check out for things like consumables, but not for big appliances, for instance.

No need for manual checking of which products pass the test, it would still be automated.

I see you bought an oven, would you like to buy another oven?