I interpret the image as saying: (some) religious people believe all answers worth knowing have already been revealed to us, and can only be found through study of the same few religious texts written hundreds of years ago. So those religious people don’t necessarily feel they already know everything, but they are convinced that the religious texts are the source of all knowledge.

I don’t know enough about Islam to claim that this applies, but it certainly applied to Christianity up until the enlightenment: there was no point in doing experiments to find out more about the world, the answer was already in the Bible. If you couldn’t see it yet, you needed to study the Bible more.