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 seems like something you should have informed your customers about a few years ago when you implemented the bell. Like whenever you make a significant change display it on a splash screen front and center, not just unload it on people and expect them to figure it out.