The major annoyance with that is that you have to explain to your parents/friends how to do that when you give them access otherwise they won’t find your stuff in the ocean of media plex is trying to push at them.
I picked Emby for many reasons and one being local accounts I control. Plex pushing you to use their accounts (and then pushing streaming content like this) just wasn’t an option.
Also plex suffered a hack that compromised online account user logins.