Compared to the height of Roman civilization, the world did really ‘go dark’ for quite some time, as de-facto warlords ruled small patches of territorry constantly warring amongst each other. It was not until the reneissance that the light of civilization truly emerged agian.
This is simplistic.
There was a Carolingian Renaissance in the IXth century which united vast swaths of Europe under a single government.
Italy in the 1100s and 1200s enjoyed a standard of living far above that of the average Italian of the Roman period.
The "light of civilization" was doing quite well long before the Renaissance.
Surely you are familiar with Anselm? Or Dante? Or Cimabue? Or Giotto? Or Machaut?
Long before the Renaissance, medieval Europeans had created complex financial and legal systems, composed breathtaking polyphonic music and engaged in philosophical speculation far above the accomplishments of the late Roman period.
Did you go to Harvard? That’s the kind of history they teach. In many respects the Renaissance was a period of decline, as a result of the Black Death. the Muslim invasion of Europe, the decline of papal authority, and the Hundred Years War.
There were peoples living among ruins made with more advanced technology than those then-contemporary peoples had available to themselves. Writing was preserved largely due to the work of: monks and clergy; Byzantine (East Roman Empire) people; and....duh, duh, duh, MUSLIMS in the roughly half of the Roman Empire which fell under Muslim rule. Some things, such as Greek fire, now have only conjectures as to what they were, because so much was lost.
Some technological progress was made (though even things such as cannons and the printing press were imported technologies), but--as you've pointed out--the Renaissance was largely when the European peoples of the former Roman Empire re-learned Roman technology and then advanced from there.
Right, key the classical music.
"The World" did NOT "go dark", only parts of Western Europe. The Eastern Roman Empire whose capital was Constantinople did pretty well during Western Europe's "Dark Ages", until it was finally overrun by the Muslim Turks in 1453