Google has justconfirmed
it will kill off another of its obsolete chat service – YouTube messages. The decision is probably related to the fact that not many people are using the ability to message directly on YouTube.
Although it's a relatively old feature having been launched back in 2017 after one year of testing, Messages on YouTube will no longer be available after September 18. The announcement mentions that since the feature was launched two years ago, YouTube focused on public conversations with updates to comments, posts, and stories.
Even though the ability to direct message on YouTube will no longer be available after September 18, you will still be able to share YouTube videos by heading to the video watch page, clicking Share, and then tapping the “social network icon” from which you want to share a video.