May understanding, knowledge and wisdom increase as ages and centuries roll along, and greatly and vigorously flourish, in each and all, in the individual and the whole Church: but this only in its own proper kind, that is to say, in the same doctrine, the same sense, and the same understanding. Vatican Council I, Session 3, Ch. 4, para. 14, Apr. 24, 1870
You seem to have missed the BUT in the quote. Sure there is development of theology apologetics but not Doctrine. "One Faith One Lord One Baptism’. Revelation ended with the death of the last Apostle.
I have read Newman’s Book but maybe with a more critical mind.
He definitely thought we create Doctrine as time goes on it is the whole tenor of his book
“That the increase and expansion of the Christian Creed and Ritual, and the variations which have attended the process in the case of individuals and churches, are necessary attendants on any philosophy or policy which takes possession of the intellect and heart, and has had any wide or extended dominion; that, from the nature of the human mind, time is necessary for the full comprehension and perfection of great ideas; and that the highest and most wonderful truths, though communicated once for all to the world by inspired teachers, could not be comprehended all at once by the recipients, but, as received by minds not inspired, and through media which were human, have required only the longer time and the deeper thought for their full elucidation. This may be called the Theory of Developments .”(pg.27)
“…Thus we see how, as time went on, the doctrine of Purgatory was opened upon the apprehension of the church , as a portion or form of penance due for sins committed after baptism: and thus the belief in this doctrine and the practice of infant baptism would grow into general reception together.”(pg. 107)
Pope Pius X condemned his idea in Lamentabili Sane, July 3, 1907–
#22. The dogmas the Church holds out as revealed are not truths which have fallen from heaven. They are an interpretation of religious facts which the human mind has acquired by laborious effort.–condemned.
He claims that Purgatory was not believed from the beginning. Then why did the Church have masses said for the deceased from the beginning? Why were infants baptised from the beginning of the Church? This is a horse that wont run.
His guidelines for true and false developments were a joke; no sane Catholic could take them seriously.