You’re not wrong that server admins could see that activity - I did mention that in my post. I’d say the process for sharing between admin\user was pretty explicit about activity being visible to the admin and it is a very direct and personal action to join someone’s personal server. I think there’s a difference between a company collecting data about user activity for various uses and a self-hosting server admin inviting an IRL personal relation to their server and knowing - if they want to go look - that they watched Roger Rabbit via a Roku device on Thursday.
I do think some of the furor is a bit out of proportion and there’s misinformation\confusion about the options - this post from OttoKerner does a good job covering the relevant options - but I think a lot of that goes to how Plex handled this poorly and the focus should be placed there rather than people’s reaction to it.
Edit: When I say “out of proportion” I only mean that Plex is a company with investors and a profit margin and such and that the “old” Plex is gone so tempering expectations for current Plex might be helpful. I know I have… 
