Why can't they fix this? It'd be extremely simple to implement basic logic to prevent recommending you the same songs you've already listened to over and over again - or even perhaps give you the option to prevent recommending you songs you've already listened to altogether. But as it is right now, there is no way to customize your recommendations other than selecting "not interested" on individual videos/channels.
How is Youtube's recommendation engine this awful? How come you still can't search for and queue up your next video while you're playing a video? It's not exactly rocket science to fix these. Isn't Google supposed to have the "best" engineers?