I did shared care with my GP for my first pregnancy and it was great I loved my GP.
For my second and third pregnancies I did case load and it was amazing. It's your own personal midwife who takes care of you and bub throughout your pregnancy. I loved the entire experience and would recommend it to anybody who asked. I would rave about my experience with the public health system in my area.
As for them asking you intrusive questions, it's their job, they have to do it. It is to monitor for PND risk factors, triggers and symptoms. It alerts them to any issues that they might be able to help some women with such as social workers, housing, dv etc.
Unfortunately the antenatal clinics can be inundated with women and bubs and this is when people can feel like a number. I'm sorry you had a bad experience.
Perhaps you would benefit from the assistance of a student midwife? They would care and be interested in your individual pregnancy.