Pre-Mosaic oral survival was brief — and extraordinary revelation filled the gap
Rome replies: from creation to Moses, heavenly doctrine was kept by oral tradition alone — so why not apostolic traditions for sixteen hundred years?
Answer: before Moses sacred teaching did survive unwritten for a while — but only among very few.
Among most it was soon corrupted and wrapped in absurd fables; God's covenant and saving doctrine nearly remained in Abraham's family alone while the rest of humankind turned to idolatry and invented cults.
What Scripture later supplied was then filled by frequent divine appearances and familiar talk with the Patriarchs, by which God repeatedly restored the viva-voce teaching and called it back to purity.
Those extraordinary appearances and conversations have long ceased in the Church.
Latin
XXXIII. At, inquiunt, adversarii, a mundi creatione ad Mosen usque doctrina coelestis per solam traditionem sine scripto conservata est. Cur non ergo similiter Apostolicae traditiones ab Apostolorum temporibus ad nostra usque tempora per mille & sexcentos annos servari potuerint? Sed ad istud dico ante Mosen quidem doctrinam sacram sine scripto aliquandiu servatam fuisse. Verum intra paucos admodum. Nam apud plurimos statim corrupta est, & absurdissimis fabulis involuta: ita ut Dei foedus, & doctrina salutis, in una fere Abrahami familia remanserit, reliquum vero totum genus humanum ad idololatriam & commentitios cultus deflexerit. Adde quod tunc temporis defectum Scripturae supplebant frequentes Dei apparitiones, & familiaria cum Patriarchis colloquia, quibus doctrinam viva voce traditam apud ipsos saepius instauravit & renovavit, eamque non tam incorrupte a piis etiam servatam ad puritatem suam & integritatem revocavit. Sed divinae istae apparitiones, & extraordinaria Dei cum hominibus colloquia, in Ecclesia pridem locum non habent.