You keep writing as if everyone has a meaningful choice about who gets data about them, but clearly that is not always the case. Someone may obtain data about someone else from a third party, and you can't avoid sharing a certain amount of data and still function as a normal member of society.
The idea of absolute, black-and-white privacy, where either you share personal information or you keep something completely to yourself, isn't very useful in the modern world. Our conventions must be more nuanced than that, and in practice that means what really matters is who gets access to data about you and what they're using it for.
That means basically don't share them with anyone, don't sign any contracts, don't work and live in the street. Because even your employer or real estate agent can sell them to anyone else in your model.
The gdpr makes people think that they don't need to think about what they share and with whom. Do you really think companies are going to significantly change just because of this? I highly doubt it. Sure there will be some things, but in the end many of the same patterns and uses will emerge.