The winners wrote the history — the losing books are gone
The objection
Widely received is measured after the fact, by the people who did the receiving. If a movement had been read broadly in the second century and then lost, its books would have stopped being copied, and after a few generations of that they would simply not exist. We would then find the surviving books everywhere and conclude they had been universally accepted — which is a conclusion produced by the survival, not evidence for it. The whole criterion is circular, and it is circular in a way that no amount of reading the fathers can fix, because the fathers are the winners.
The response
This is a serious methodological point and it cannot be answered by insisting the fathers were sincere. It has to be answered with evidence that survives independently of the winners' curation, and some does. The discoveries at Nag Hammadi in 1945 handed us a library of exactly the literature that supposedly vanished — and what it contains does not look like a suppressed rival mainstream. Early Christian papyri turn up in Egyptian rubbish heaps, discarded rather than curated, and what is in the rubbish is overwhelmingly the same books, which is a sample nobody selected. The opponents' own hostile summaries survive: writers refuting other groups quote them at length, which preserves their content in a form the church could not quietly edit. And the second-century writers arguing against these movements plainly regarded them as recent, which is testimony from people close enough to the question to be wrong in a checkable way. The objection remains partly standing — we cannot fully reconstruct what did not survive, and that limit is real. But the picture of a lost, thriving alternative Christianity erased from the record is not what the independent evidence shows.