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.
The Renaissance didn’t bring about a rediscovery of Roman technology. That has been on-going for several hundred years. The foundation of modern sciencve was laid during the Middle Ages. There were more machines in western Europe than in all the Roman Empire of the past. Greek science had been making its way into Europe since the 11th Century, with the beginning of the Crusades and the restoration of the old trade routes.
Re: Acts, I always thought, it referred to temple sacrifices.