“would we see a worldwide slide back into the Dark Ages? ”
No..there are to many printed books and educated people for a total record keeping fail. The Dark Ages were a transition period created by a lack of literacy in Latin. The long established schooling of wealthy citizens dwindled as the Roman Empire slid out of control. Romans were fastidious record keepers and that is what allows us to know about that period. European’s had some latin scholars but not enough to keep great records. Eventually the use of Latin was limited to the church.
Culture didn’t necessarily decline, the accumulation of capital by one authoritative entity ceased. The lack of records and recored historical information create the darkness.