After a university in another state sent me an unsolicited email offer (never opened), my google feed started showing me everything about that school, even going as far as setting up notifications for its class registration calendar. The feed started to loop in college football and greek life news, which are incredibly off base for my actual and actively searched interest history.
I spent a year slowly cultivating a pretty decent feed of relevant content on my Pixel, and it went full Netflix 2010 seemingly overnight.
Early Netflix suggestions, no matter how selective and consistent your selections over many years, could be instantly subverted by your lonely sister-in-law getting on your account one Saturday night and watching a few foreign language romance flicks. After that, you'd never really stop getting recommendations for "movies starring sexually aggressive male leads" or "films with actors who look like Antonio Banderas".
I think I'm done being used to train everyone's algorithms.