Only problem is, These were not “new” teachings, only further defined.
If this is true, you have no problem. However, an always-believed teaching will be defended from denial at any time in the Church’s history (in fact, continuing opposition to such denials leads to the teaching being dogmatically defined). With the teachings of Papal Infallibility and the Immaculate Conception, we don’t see this opposition to denial. In both cases, the new opinion begins as an extension of a true teaching, is opposed by some and accepted by others and eventually gains prominence and is promulgated as truth and this is when the denials become inadmissible. Once again, this is how heterodoxy spreads and becomes established, not an example of the history of orthodoxy, which doesn’t arise in certain centuries and has to wait until another century until its denials are condemned.
These were also not foreign concepts out of thin air as you like to make them out to be. Your own liturgy proclaims Mary to be spotless doesn’t it? (not sure exact wording)
This seems like a rather loose and easy way to approach Church teaching.

All kinds of teachings can arise with a claim of being similar to an orthodox teaching. It is not enough that a teaching has a similarity to a true teaching, but that it is actually true, itself, as all heresies have the appearance of truth. And the chief way we discern a true teaching is whether it can be traced back to the apostles (a test the Fathers could only advocate if it were possible to observe the teaching being taught from the beginning). Besides, it is correct that the Most Holy Theotokos is spotless. However, this doesn’t mean that she was free from original sin, as original sin doesn’t entail a stain of guilt in the Orthodox Faith. Since the West developed a more guilt-oriented understanding of original sin, I can see why the teaching of the Immaculate Conception would develop in the West as an attempt to maintain the new understanding of original sin and the oft-repeated affirmations of Mary’s spotlessness and purity. However, that didn’t stop many Western saints and religious, including St. Bernard of Clairvaux and Philip of Harvengt, the Premonstratensian abbot of Bonne Espérence, from censuring the new opinion of Mary’s Immaculate Conception as being wrong since it excluded Mary from the general transmission of original sin (which they, like Orthodoxy, believe passes generally to all men, regardless of whether it is entails guilt or not).
Btw, do you believe God must adhere to some man made time table? Is He uncapable of revealing the fullness of a Truth when He so chooses?
It’s not that God is incapable of this, but that the Fathers and the consciousness of the early Church show that God didn’t intend this. It isn’t difficult to discern why the Lord wouldn’t intend a progression of revelation and acceptance of the apostolic Faith of the Church (as opposed to a better understanding of the constantly-affirmed Faith, which is acceptable), as this would paralyze the response of the Church to heretics, as there would be no clear way of knowing whether these men would be teaching heresy or instruments of developing Church doctrine. In addition, it would make the Church incapable of giving the fullness of apostolic teaching to all people of every age, thus giving Christ’s Great Commission a partial application. Read these words of St. Leo, Pope of Rome in response to the various heresies of his day:
“
And you must so diligently exhort the laity and clergy and all the brotherhood to advance in the Faith as to show that you teach nothing new but instil into all men’s breasts those things, which the Fathers of revered memory have with harmony of statement taught, and with which in all things our epistle agrees. And this must be shown not only by your words but also by the actually reading aloud of previous statements, that God’s people may know that what the Fathers received from their predecessors and handed on to their descendants, is still instilled into them in the present day” - Letter CXXIX, To Proterius, Bishop of Alexandria.
This quote, which merely reaffirms the unanimous teaching of the Fathers and Saints of the ancient and modern Orthodox Church, reveals that God did, indeed, ordain that His Truth would be known and taught by all generations and that the faithful should use the standard of their ancestors’ faith as the basis of their own. This rules out any new beliefs like Papal Infallibility and the Immaculate Conception from developing in the Church, if they cannot be shown to be part of the known and proclaimed Faith of our Fathers.
God bless,
Adam