DF Tube (Distraction Free for YouTube™) (https://tinyurl.com/yd3x2lag) is a Google Extension that is used to hide the video recommendations sidebar and the related videos that appear at the end of videos. It also removes the grid of recommended videos that appear on your homepage. All of the settings in DF Tube are configurable and allows you to hide comments and disable playlists sitewide.
YouTube™, as a company, is directly incentivized to create views and get as many ad clicks as possible. Because of this we are often overwhelmed with thumbnails and advertisements from every angle. While this is good for someone looking to kill time, it is not so good if you are trying to focus on educational content, do research, or find some relaxing music to groove to.
Give it a try for yourself and see how much more productive you can be!