This is so not true... For the whole Middle Ages people rarely could write, but still there were lawyers (yes, lawyers who could not write), doctors, scientists, poets, merchants, mighty and clever kings (yes, there were kings who could not write). Middle Ages gave us crucial inventions that built European civilization (mills, windmills, agriculture inventions like three-field system, ships building technology and so…
The problem is geography. France, Britain, Germany and such were never part of the ancient world. Rome had colonies there. But, these were (relatively) short lived outposts of civilisation. Civilisation was never a dominant culture in non-Mediterranean "Europe."
In the East, civilisation existed for thousands of years before Rome. They always had roads, kingdoms, bureaucracy, restaurants, banks and such. Even in dark ages, after collapse... these were collapsed civilisations. They didn't revert to tribal, oral societies.
The european Renaissance (excl Italy) was never a Renaissance. It's the actual birth of civilisation in europe. It's the first time writing became a major thing.