How to Delete Unused Content

I need a way to delete all unused content. It's extremely difficult to sift through all the content that has ever been uploaded, and to compare similar images/videos for file size differences. Even in the list view it does not show file size. 

I've seen posts from years ago, in disbelief that this type of filter has not been developed, especially for a website building program, but maybe things have changed or someone has written a third party script.

This is essential. Any input? Or just another massive SS miss?