I don't really think there's a whole ton to say here, honestly. There exists a huge quantity of copies of older artistic works in almost every medium today, such that I would not be surprised, though I doubt that any statistics on this could possibly be compiled, if the amount of copies of a single Michelangelo (for example) in existence at this exact moment is larger than the quantity of all art sold in the past century, if not much longer. These modern copies of da Vincis, Rembrandts, Venuses, and so forth exist because art students copy them as part of their instruction, enthusiasts copy them for their own purposes, and lithographs and other types of copies are produced for the wider market that cannot, obviously, get their hands on a unique work of sculpture or painting but nevertheless want to be able to look at a da Vinci or Vermeer sitting over their fireplace. Yet no one would suggest that contemporary artists have lost their ability to innovate just because there exist more copies of Kandinskys than Kandinsky's total output. If we were to order the burial of all works of art globally right now, I have absolutely no doubt that almost invariably pretty much only the copies would be unearthed some hundreds of years later. It's the same thing for antiquity. Student sculptors learned by making copies, sculptors with their own shops made money by making copies of famous Greek sculptures for the Roman market that wanted a discobolus but obviously couldn't provide an original for more than one person. The large proportion of these copies that come from the Roman Period is more a reflection of the massive role of the titanic Roman economy, and its ability to trade in luxury goods across the Mediterranean to a degree unrivaled until the early modern period, than anything else.