I don’t agree, obviously.
The Trinity, as we know it today, was unknown for years after the resurrection, but the Truth of it existed hundreds of years before it was known.
The Apostles never taught it, nor did they even try to explain it. We have no clear idea of what or how the Apostles thought regarding the Trinity, but we can find the Truth hidden in Scripture.
Hundreds of years after the resurrection, there are those who deny the Trinity, who do not know this truth. Does that mean that it is heretical since we cannot find any explicit teachings on it in the NT?
The trinity was implicit in Scripture. The Marian doctrines and other novelties are derived out of whole cloth, many times from heretical documents.
How preposterous. It was well known and understood from Jesus teaching. Even the apostles called Him God. He said He was the “I am”, and it was His Holy Spirit that was sent as councilor which was clearly understood by the apostles and all they taught.