If a message is public then I shouldn't care if Meta has access to it or not; they can access it if they want to do. However, if I wish to send a private message to someone, even on a different server, it should not have to go through Meta to do so (unless the recipient is on Meta, although then the sender should be made aware of that before sending the message).
I don't use Fediverse nor Meta/Threads, but I write stuff that is public and anyone can view it, or private which only the recipient should read, like anything else, whether I post on Hacker News, or on Usenet, or on a public IRC channel, or whatever else it might be. (Some people don't like public IRC logs, but if it is a public channel then I would prefer that it does have logs; fortunately some IRC channels do.)
IME the problem with Meta in the fediverse aside from the privacy issues is that fedi is largely built by and run by people who want a community separate from the mainstream of social media, with their own rules and goals, without corporations, for them specifically and not for profits.
I don't use Fediverse nor Meta/Threads, but I write stuff that is public and anyone can view it, or private which only the recipient should read, like anything else, whether I post on Hacker News, or on Usenet, or on a public IRC channel, or whatever else it might be. (Some people don't like public IRC logs, but if it is a public channel then I would prefer that it does have logs; fortunately some IRC channels do.)