If you're trying to imply counterfeiting doesn't actually affect gameplay, counterfeit cards are not tournament legal. If you paid $100 to purchase a playset of 4 cards and you show up to a tournament and get declined entry, you'd rightfully be pissed at the counterfeiter.
Maybe the next response to that is "who cares about tournaments. Just play kitchen table magic with your friends." In that case sure, but still don't use counterfeit cards. "Proxy" cards are when a player prints out (or even hand-scribbles on paper) the image of the "real" card they want to use. No one is scammed out of money. It doesn't cost anymore than a sheet of printer paper and some ink. And because the card is obviously not official, there's no confusion as to it's authenticity.
I play MTG competitively, and if you actually believe this is a thing I'm afraid you have no idea what you are talking about. No competitive game has ever, at any point, worked that way.
From a gameplay perspective, the problem is exactly what your parent said: counterfeit product cannot be used in a sanctioned tournament. Which means most MTG organized play, since even very small in-store tournaments are usually sanctioned events.
Maybe the next response to that is "who cares about tournaments. Just play kitchen table magic with your friends." In that case sure, but still don't use counterfeit cards. "Proxy" cards are when a player prints out (or even hand-scribbles on paper) the image of the "real" card they want to use. No one is scammed out of money. It doesn't cost anymore than a sheet of printer paper and some ink. And because the card is obviously not official, there's no confusion as to it's authenticity.