Things could be encrypted. But yeah, that's my biggest issue with the fediverse, it's just not designed around privacy. It's also why I'm working on my own lemmy alternative, I want something a bit more privacy-friendly.
I don't think working on a LinkedIn alternative is worthwhile because it relies even more heavily on the network effect. The only point I see in LinkedIn is in finding jobs, and getting employers to look at something else is an uphill battle I don't want to fight.