It's rather dumb that I have to get a plugin to un-attach media in the first place, but that's a WP shortcoming (which people have complained about for years now).
This plugin will let you un-attach your media as advertised, just like the other two (at least) plugins out there. But if you have a lot of media to un-attach, you will be clicking all night. Not one plugin lets you un-attach more than one. 3/5 for doing the bare minimum and overlooking the obvious.
Frustratingly, lack of batch functionality is a limitation I run into frequently in the WP world.