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.
Maybe it’s me but us content creators are the ones that know what’s best for our content including how to market it. Focusing on the hot mess that is the site layout would be a better use of resources.