There can be development of doctrine.
No, doctrine doesn't change. There can only be developments in the UNDERSTANDING of doctrine, since doctrine is essentially a Divine Truth, which is never fully understood by humans, since it's a mystery; therefore the Church, through Her saints/doctors can add explanations, as long as the doctrine remains essentially the same. Doctrine must be understood the same today as yesterday and tomorrow (since all Doctrines of the Church are part of Tradition, at least implicitly, and have been held since Apostolic times).
This contrasts to the last 150 years where modernists have tried to change the meaning of doctrine, just like at V2. This isn't possible.
p.s. John Neumann wasn't completely Orthodox. Take his writings with a grain of salt.