The decline and fall of the Dark Ages (as a term of historical reference) is quite a fascinating phenomenon, although perhaps not as complete as some people believe. Articles like
this one might lay into a variety of straw men, deriding 'pseudo-history' in a pretty pseudo-historical way, but a scan through Google Books reveals quite a few recent titles of varying degrees of academic worth that still use the term, albeit often in 'scare quotes'...
I believe earlier writers - Gibbon in the 18th century, Burkhardt in the 19th - tended to use the term to describe the entire period between the fall of Rome in the west and the renaissance. By the mid 19th century, it had settled into its more familiar meaning, describing the immediate post-Roman centuries in western Europe specifically.
As such, it's still quite useful. Even leaving aside the negative associations of 'darkness', and considering the more nuanced appraisal of the era provided by recent archaeology, this is still a pretty
obscure period in european history, at least from our perspective. The entire literary output of the British Isles between AD400 and 700 appears to have amounted to less than that of a single year at the height of the Roman empire. Perhaps less than that of a single day during the late republic.
Literature isn't everything (although it leaves us a bit clueless about what might have been going on), but material culture also sees a decline. The principia of the legion fort of York, for example, still had paved floors and functioning heating c.AD400, but within a hundred years had apparently been turned into a pigpen, a slaughterhouse and an indoor cemetery. It would take a considerably lateral approach to value judgements not to see this as a decline in local living standards.
I was looking through Ward-Perkins's
The Fall of Rome and the End of Civilisation recently. He gives some interesting pros and cons to the use of 'dark ages', 'early medieval' and 'late antiquity' as descriptors. While it's true, he says, that both 'dark age' and 'medieval' have unfortunate connotations today (nobody in a popular movie has yet threatened to 'get late antique' on anybody's '@ss'), the positive emphasis of 'late antiquity' tends to focus too strongly on religious and spiritual developments, and neglect the social and cultural.
This in turn, W-P suggests, is part of a wider desire to rid history of notions of crisis, violence, and decline. Admirable as such a desire may be in relation to the present day, it threatens to diminish our ability to understand the violence of the past, and to see it in context. By extension, it replaces one set of mistaken images (hairy barbarians trashing the glory of Rome) with another (evil Roman proto-nazi oppressors overcome by the freedom-loving ancestors of the modern world)...
(It might be worth mentioning, of course, that plenty of Romans believed themselves to be living in a 'dark age' - either comparing their times with the great days of their distant ancestors, or, like Cassius Dio, claiming that
our history now descends from a kingdom of gold to one of iron and rust.... ;-) )