The arguments I've heard about tracking etc are misguided and don't understand the actual risks.
Firstly, posts on the fediverse are already likely being consumed by advertising platforms like Facebook & Google. It would be trivial for big tech companies to setup relays that act as scrapers.
Secondly, the value in platform's tracking individuals is for advertising. There is no mechanism for these platforms to identify you browsing the we if your instance federated with threads. Your instance won't share cookie sessions etc with threads. It doesn't increase your exposure.
Thirdly, these platforms have the know how to deal with spam and they will be incentivised to share that tech with other federated instances.
Don't get me wrong, Facebook is an evil company. But I haven't heard a decent argument as to why them joining the fediverse is a bad thing. We always have the option to defederate in the future.
Change my mind.
Pablo Escobar did a lot of great things in his local community. Many considered him a great guy. He's the Facebook of Columbia. Meta is a predatory shit company that would put everyone in a suicidal depression to make a dollar. At least Escobar's products had an up side for some people. Meta has no ethics. Only a fool invites a serial killer into their home because they like your new kitchen knives and want to have a look.