The “dark ages” is a myth thought up by Gibbon and other 1700 and 1800 authors who blamed christianity for the fall of Rome
They forgot that
1. Scientific discoveries still continued by monks etc. until the Arabic conquests cut off North Africa from Christian civilization
2. The Eastern Empire didn’t fall until 1453 and continued development
There were no “Dark Ages” - there was a slight interregnum between 451 and the Carolingian renaissance in 800 AD but the knowledge was never “lost” - the Eastern Empire kept it. In fact we shouldn’t even call it the “Eastern Empire” - it called itself the Roman Empire
The Western Empire was due to fall under the onslaught of the Germans, but even these Germanic peoples were content to keep the structure below the same and just skim off the top - why kill the golden goose?
The real delay was islam.
Even in the Roman Empire of the 7th and 8th centuries they still were convulsed in philosophical discussions rather than practical science.
The real push for scientific development was the breakdown in the Western world - with competing countries competing with each other for more discoveries.
I think the people who suffered through the nearly 1000 years of the dark ages might differ if they had known what had been lost after Rome and how much more dismal their existence was as a result. It is literally true that human beings in Western Europe lived better in the Roman Empire then they did at least until the 19th century. The water was pure, the sanitation was better, diet was more varied and there was clearly less anarchy. There was Roman law and a common language. The squalor, barbarity, insularity and insecurity of the dark ages truly made life nasty, brutish and short.
The Carolingian Renaissance was very short-lived, expiring almost with its namesake.
I take your point that the knowledge was not lost, it was however precariously tucked away in Rocky crags along the Atlantic coast and, to some degree, in the Eastern Empire and in Islam until destroyed in Alexandria.
I take your point as well about the dark influences of Islam. The argument is that the Pirates of Islam shut down all commerce on the Mediterranean and so pitched northern Europe into a catastrophic depression as it extinguished virtually all Mediterranean commerce.
I think this is probably true, although I am not thoroughly educated on the subject and especially ignorant about the gap of at least 200 or 300 years between the fall of Rome and the conquests of the Mediterranean by Islam beginning no earlier than 620 A.D.
I would like to have your thoughts on this as well as the rest of my propositions.

The "Dark Ages" were actually pagan in character -- the relatively massive waves of new settlement and carving out of fiefs all over western Europe, including the entire British archipelago was pretty much all pagan. The pagan "Dark Ages" began before the "fall of Rome" in the west and ended at different times in different places. I think the "Dark Ages" as visualized by Gibbon was more about being an Anglophile than about anything else.
The eastern Roman Empire had its ups and downs, but lost all authority over western Europe after one of its peaks, under Justinian. That died of too many taxes and the Plague.
The other day an article about a new breakdown of the strains of plague in Europe caught my eye, now I can't find it. Now, back to the real post...
OTOH, in the late 50s to mid-60s, the dig at Cadbury in England turned up a large "Dark Ages" settlement, post-Roman, but with artifacts that had resulted from trade with the Roman world. Same has been found in other sites in Britain, including Tintagel (once someone got around to doing serious work there).
European feudal society was more like than unlike the society of Rome, but got stuck in a system with very little upward mobility, ruled by a hereditary hierarchy.
The Renaissance arrived because of the 14th c outbreaks of the Plague, which destroyed so many of the traditional practices -- labor became valuable to the laborer; the practice of law became more systematized; trade became more wide open; national identity and ethnic consolidation rose to dominance; and my personal favorite, the use of gunpowder completely changed warfare -- and private lending (which was all that Rome had ever had, apparently it worked fine) transformed into what we'd call international banking, led by the Medicis, who also bankrolled the artistic and scientific renaissance in Italy.