On Android and iOS, the YouTube app appears to have gained a new video player UI that includes all major components in full-screen mode. A row of icons has been added to the bottom left corner of the page, which appears to be a server-side update. On the left, there are like and dislike buttons, as well as a quick toggle to the comments, save to playlist, and share buttons, while on the right, there is a more videos tab that displays recommended content. The listening controls tab is also included in the midst of music videos.
The new UI was tested on an Android 12 smartphone running the YouTube app version 17.03.35. You can still dislike videos, but you will not be able to view the counter. The new controls give you a lot more power when watching full-screen content, and they eliminate the need to reduce the video to engage with crucial tasks.