When a person hits that subscribe button they are saying, I want this person's content... not I want you @Youtube to decide what portion of content I get.... C'mon guys, to subscribe is an action, which means that sub is saying, give me this content
pic.twitter.com/ie8N97VQzF
This isn't difficult. Someone subscribes to a channel they receive all notifications of new content. You notice over time they consistently don't watch the content you throttle back on notifications. Strange how my recommend is always full of big YouTubers I never actually watch