I think the fediverse does have a privacy problem, however as long as your account can’t be linked to you (malicious instance, your email being breached) it doesn’t matter all that much (at least for my threat level) because the info is confined to the fediverse, where little can be done with it, especially if you swap instances/accounts commonly. Yes, one could create a profile on you based on what you upvote/downvote, but they can’t for example use that to serve targeted ads, because the fediverse doesn’t have a ad network and when visiting other sites they can’t associate your profile with you (assuming you don’t reuse your username), unless I am forgetting something.

tldr: The fediverse isn’t private, but the data is practically useless

i mean it’s in the name:
FEDiverse

Ones like Lemmy fit in fine to my threat model. They enable me to use privacy tools up-to-and-including Tor routing, without a phone number or other personally identifying info (you can’t do those with many other social media platforms). I can use the Fediverse pseudonymously, and if I ever want to, anonymously.

I’m not hiding this conversation from you, but I am hiding my identity from companies.

obviously public fora content is not meant to be private but using a fedi instance is privacy focused solution vis-a-vis redidt who tracks ever fucking click and finger prints your browsers while permittitng rando creeps like sundar and faceberg to do the same.