If you disable the app on Android, that should prevent the app and all associated services from running. It should also uninstall all updates that were applied above the version installed to the system partition. There’s no reason to believe that Facebook has higher privileges than other system apps. If you don’t trust the OS on your phone on the other hand, then there’s really no hope.
Ultimately, I think the competition here will come from services like Mastodon and Diaspora. As mentioned in the original post, the greatest value that Facebook provides its users is connections to other users. Leaving Facebook means losing access to those users. Leaving one instance of Mastodon or Diaspora doesn’t force you to give up access to all of those users, since you can access them from another instance.
