As soon as you mention UI design people immediately start thinking about how it looks and how impressive it must be. Of course it is important that the UI is nice and has a modern look. But the most important thing about UI and UX design is not how impressive it looks, but how easy it is to use and how well it works for selling new services and presenting content to the customer.
The UI itself should never be center stage, it should be the guide that the user can rely on when navigating content and an entertainment experience that is increasing in size for every new service that is added. That way the user will be more eager to explore than afraid to leave their comfort zone.
This also means that the UI itself must take a step back and provide the user with some, sometimes expected, basic needs. The TV user is pretty conservative and things have been the same for decades, the channel listings, the way you expect the remote control to work, the number of actions involved etc. And if these standards are broken, the UI must be very clear on explaining why and how this works.