Premodern traditions of knowledge such as Islam, Christianity, Buddhism and Confucianism asserted that everything that is important to know about the world was already known.
The above is missing an important context: known by whom? Regarding worldly knowledge, this is what the Buddha said:
Once the Blessed One was staying at Kosambi in the simsapa1 forest. Then, picking up a few simsapa leaves with his hand, he asked the monks, "What do you think, monks: Which are more numerous, the few simsapa leaves in my hand or those overhead in the simsapa forest?"
"The leaves in the hand of the Blessed One are few in number, lord. Those overhead in the simsapa forest are more numerous."
"In the same way, monks, those things that I have known with direct knowledge but have not taught are far more numerous [than what I have taught]. And why haven't I taught them? Because they are not connected with the goal, do not relate to the rudiments of the holy life, and do not lead to disenchantment, to dispassion, to cessation, to calm, to direct knowledge, to self-awakening, to Unbinding. That is why I have not taught them. ~~ SN 56.31 ~~