This line of thinking presupposes that there were no arhats, no practicers of dhyana, no ascetis, no living bodhisattvas,
One's beliefs about their expression in this world may vary greatly. This is a little strong in statement.
This line of thinking presupposes .... no persons who had attained the psychic masteries, the supernormal powers, the five eyes etc... who possed oral instructions, who could see past, present and future like the palm of their hand. !
Omniscience is arguably the ability to see the eyes with a heart that knows the essential empty nature of things. That is the great one thing worth knowing because all things take place within it. Because people of various grades of matured mind use the same words in tales that describe BOTH the Formless and the Formless Worlds, (so we need metaphor - fantasy element to make invisible things visible) , different levels explanations naturally arose and continued side by side, explanations displaying different assumptions of of metaphorical literalness.
The fate of all things lays within the truths of coming together of persons and objects due to causes and conditions, their persistence driven by habit formations and the fruition of karma, and their eventual dissolving. Details like which disease gets you or which day you die are trivial details of relevance only to fictive ego viewpoint. That viewpoint of science is that in which the metaphorical language of sweet Dharma skillfully wrought tales is understood to be just that.
IN MY OWN OPINION ONLY: Those tales were told to reach out to everyone of all levels of metaphorical self imagining.QUESTION:
Instead it supposes that suddenly there appeared a book club that sold Mahayana sutras, which had no contact with anything that really existed!! Can you not see that these books would have no authority at all !
IN MY OWN OPINION ONLY: No, don't lose heart - many were transformations of suttas, others to a new perspective were visionary soundings from the ground of bodhisattvas that tasted the same echoes of the dharmakaya as the Shakyamuni so as a 'buddha-ground hearing folks, followers in his footsteps', spoke continuing his voicing of the voice of the ground of Buddha nature.
In the growing consensus of academic study, "Book Clubs" actually light hardheartedly describes the monks and nuns new wave of Mahayana mindset living in traditional monasteries meeting to have study and worship centered on these new texts. The struggle of people to evolve is neither trivial or disappointing placed next to carnival wonders.
IN MY OWN OPINION ONLY: Letting go of the worldly metaphors carrying non-cognitive buddha realization is one that is incremental and can be a stressful and painful and these nyam or phenomenon are a feature of the path of effort.
There is no substance in self or phenomena. All metaphor of World and Contents is mind-construction.
IN MY OWN OPINION ONLY: So the pith of all metaphor is silence. AND The heart of all faith is kindness. To living deepening in knowing the truth of this - this is the Buddha's intent.