I get you are probably being purposefully derisive to make a point by saying the name of the dark ages is because of our ignorance, but that's also just not correct. The general consensus of historians is that Europe suffered from widespread material simplification during the early middle ages, compared to classical antiquity. The name was coined by earlier historians, generally less concerned about mixing moral judgements with scholarship, that viewed the period as less enlightened than those surrounding it.
Thats one version of why. The other version is that it ran counter to a historical narrative about the (alleged, believed) moral superiority of antiquity and so was coined to further a somewhat political goal.
I mean, you can see pretty clear evidence of sharp declines in trade and industry in all sorts of ways following the fall of Rome, such as rates of silver production tied to concentrations of atmospheric lead in Greenland ice samples. It's not just something historians made up.
A good point, and to the specificity of early post Roman to 1000AD feels like a valid measure. But you also see innovations in trade, arts and embellishments, cathedral building. I don't think the coining of "the dark ages" label had the luxury of gas chromatography, it was an adjective of philosophical value, figuratively applied as a value judgement.
