And Plex is for self hosted content. Maybe it's on the list because it's not open source but I still wouldn't put in the same group with Netflix Hulu and max.
Plex desperately wants to be more then just a self-hosted library solution, as that's often (though not exclusively) associated with piracy. They also have a free streaming service, similar to Tubi and Pluto, that can integrate with your own library.