Rather than whether pre-writing humans were poor thinkers, it feels easy to assume they struggled to build on past knowledge.

Also tbh for myself its hard to imagine a time pre-writing if we include all kinds of writing including pictography.

That they needed to continuously communicate knowledge in new ways and repeatedly to be able to build on previous knowledge. It can also highlight the importance of storytelling, fables, singing, etc.

It's misleading to compare two contexts this different. The millennium during which writing slowly evolved was optimized for orality in a way ours is not. People learned to memorize a lot more, for example. As an approximation you may consider yourself exempt from OP's generalization if you're illiterate.

I believe there was an oral tradition in place to keep track of important events in certain cultures.