Ads that are related to the page content yes, as they might be even useful (eg book suggestion). But ads about things I already bought on another website five d

Ads that are related to the page content yes, as they might be even useful (eg book suggestion). But ads about things I already bought on another website five days ago - personalised ads are both scary and useless, every single time - you are right, they are spammy and ad-networks haven't learned a bit and just followed Google with that trend ten years ago.