The algorithms are way to primitive / stupid. When I watch just one video which explains rowing to show it to a visiting friend, my stream gets flooded with rowing videos afterwards.
When I watch a video describing a new lens for a Canon or Fuji system, I get flooded with videos for Nikon or Sony stuff later on. When I choose "not interested" I only get two options a) I watched this already (which YT should know obviously, as I'm a subscriber, or b) I don't like it. A useful option like "I don't have Nikon/Sony stuff" or something more specific like that isn't available.
Amazon for example uses an equally bad algorithm, it seems to be "industry standard" ...or even worse, because the don't need to offer me another fridge or washing machine once I ordered one. Idiocracy, sigh.