“Nothing sacred about 100AD, if Paul => Titus => A => B ... => Z, then you can still have an unbroken chain of doctrinal truth and unity from the Apostles to this day.”
... and that is my point. You have a couple hundred years of a gap, during which pagansim was added to the Roman Broth.”
“If not Rome, which denomination ?”
It has nothing to do with denominations. Category mistake.
Except that churches usually identify themselves by a denominational label and doctrinal statement, although if they are TV churches, prosperity churches, and a host of other new start ups they may not have a denominational tag yet. There was no gap. There were churches in every generation. You hold that the Great Commission failed, in that paganism corrupted the churches until ... when exactly, and who exactly renewed the apostolic doctrinal truth and fellowship ?
“It has nothing to do with denominations.”
Then what teachers, seminaries or church authorities do you believe teach the Truth today or historically? And why would those who do teach with authoritative truth, in a world of a thousand or more flavors of doctrine NOT have a label or name that the faithful could trust?