Recently I learned that the supply of papyurs in Europe declined with the fall of the Roman empire around the 4th century and as a consequence the price of literature increased drastically since parchment was way more expensive to produce. Rolls made out of papyurs were basically pressed and dried fibers of the plant. Why did nobody come up with something similar only with european plants? Is this process really only possible with papyrus or were there other reasons?
All right, there's a few things wrong with this premise.
One is that it's just plain wrong, as explained by u/Noble_Devil_Boruta; there are certain virtues that parchment has as a material and some upsides unique to Europe.
Another is that this whole 'dark ages' business is also Not Cricket. This compilation should answer that thought. No era wherein pie fraud is a legitimate concern can conceivably be 'dark'.