There was always a line though between “i’m sharing this personal information with you privately” (i.e. registering with your name and e-mail address), and “I’m sharing this information with the general public”. You also were able to remain somewhat anonymous, by registering with your real name but making sure other users only saw your screen name.
While there was always the threat of someone finding your publicly shared photos or stories, the idea of the company you’re giving them to analyzing all of that private and public data, across the entire web thanks to tracking cookies, and using it to manipulate you or packaging it up and selling it.
The idea that you have zero control over how your personal and private data is used, or who it’s sold to, is terrifying.
You would like to think so, but one thing that’s become clear to me is a large number of new fediverse users are only interested in escaping what Reddit/Twitter have become in recent months, and have no issues supporting competitors who will abuse them algorithmlically just the same.