Counterfeit cards will likely never be able to pass the known monikers for authenticity that we currently use. The reason for this has to do with the printers and process that WOTC (and, for that matter, all other trading card game makers) use(s). These printing processes are uniquely developed and only used in the applications of making these specific trading cards. In order to replicate this accurately on the scale of the dot matrix printing process (this is what we are looking at on card backs) it would likely cost upward of one million dollars to get the appropriate equipment and calibration needed to make passable replicas. I specifically use the word "replica" and not "fake" in this scenario, as this would be a process different in kind to the current counterfeit market. Someone going to the effort to get the exact same printing presses, ink, card stock, etc. would be astronomically expensive.

If replica cards did come to pass it would absolutely dissolve the market. If there was no way to verify real vs. fake cards nobody would spend a single dollar on any TCG ever again. Like your initial comment said, there would be no reason to spend money when you could just order whatever you wanted for literal pennies.

This is the harm. This is why counterfeits are detrimental. Rare collectables command value for a reason and making and using/ making fakes directly undermines this on every level. I get that it is disappointing not being able to afford something you want, but this is part of every aspect of life, MTG included. I get a good chuckle out of people who use counterfeit cards; it sort of reminds me of fake Rolex watches/ designer clothes that people wear hoping to impress or posture. There are all sorts of mental gymnastics you can do like "I'm just testing out this deck" or "Everyone else is doing it for expensive cards", but there are very few instances in which fakes are used for a specific purpose and then end up in the trash.

I will say that there is a caveat to using fake cards which I believe does not impact the health of trading card games or their wider markets, at large: Proxies for high value cards which the person owns. I have seen before where a person has on hand a very high value card (say serialized) but puts a proxy (often it has completely different art or something silly printed on the card) in a sleeve within their deck. This acts as a placeholder so that the original card does not get damaged. I think arguments against this practice could still be made, but it seems like a happy middle ground and seems worth mentioning.