You are right about most, but the NSA actually did fulfil its purpose many times. I don't know if they do any more or if the majority of what they did was good. However, they used to make actual substantive recommendations on encryption and assisted with algorithms like AES, SHA2, and IFF mode 4. They also were pretty good at securing voice and data communications in the military. As far as I know, their military grade stuff has been quite secure.