I'm not sure why you were downvoted so low that I had to vouch you up; but the concept of a western intellectual dark age has well and truly been contradicted by modern scholarship.
It is contradicted by some modern scholarship, but it is by far not the consensus in the field. There are many scholars who do believe that Europe entered period of civilizational and intellectual decline for a number of centuries after the fall of the western Roman Empire. The debate is very much open on the issue.
For further reading:
https://en.wikipedia.org/wiki/Dark_Ages_(historiography)#Mod...