What device do you have? Some cheap Android phones may have "advertisements" which can reinstall some apps after deletion, but you should be able to disable that
Fediverse data is open to basically anyone. This means while you're not gaining privacy you are de-commodifying all of it as well as your product use experiance.
Many admins have already committed to blocking Threads. So if you don't want to interact with Meta/Facebook at all, just use an instance that has it blocked.
Maybe the way we deal with these tech companies is to build our own fediverse (duh) then keep giving them an ever growing list of federation requirements until they all bankrupt each other trying to take over our club.