The experience of Casting YouTube to a Chromecast-connected TV has remained mostly unchanged for the past several years. Google now looks to be making a pseudo-YouTube app for Chromecast that takes after the Android TV version. Historically, Casting a video from your phone to a Chromecast-connected television just loads a video player that provides basic details (channel name, view count, date, and time) in the bottom-left corner.
Link: Google testing Android TV-like YouTube app for Chromecast
via 9to5google.com