We are running a small experiment where 0.3% of viewers will see an auto-generated thumbnail, instead of your custom thumbnail. We are not removing the ability to create your custom thumbnail, but we hope to gain insights on auto-generated thumbnails for the future.
So you remove the option to swipe across menus on the mobile version, you make videos continue to play when you exit to your home screen, and now you're doing this moronic garbage without asking the user first. Can you guys do something to make YouTube BETTER, for a change?