Sorry to burst your unrealistic bubble, but your little Game Gear? It's likely not working anymore - with a failure rate closing in to 100% due to degraded capacitors. You will have to pay dear money, or know how to solder new ones yourself. Same thing applies for quite a number of other Sega consoles. Your (unlikely to be) beloved Jaguar CD? It is no longer working either. Some systems are more resilient, like your Game Boy, but many others are already facing real disc rot. Even then, for some of your old Nintendo games with a soldered battery, you will need to learn basic soldering to remove it and install a new one - and forget about your save file from when you were a kid. The data has long been gone. Your first few 3D0 and possibly Sega Saturn games? Might not be working anymore. The drive on your first gen Playstation? You might need to recalibrate the potentiometer if you are lucky.

My point is that the narrative that the old libraries we have still 'just work' is also false. There is a reason why retro gaming enthusiasts are increasingly having to learn general principles of upkeep and game preservation - or they move into emulation altogether as the best way to 'preserve' these games. I have a vast collection of oldies, amassed from when I was a kid in the 80s. I am under no illusion, that most of the games I have actually do not 'just work' anymore.

Question.

Did GKC ban of copied cards get solved?
I heard the used game marked is kinda dangerous. You really need to trust the seller.

I can understand the concern with the GCKs in some ways, but if we are for real, we have no guarantee that our Discs and Cartridges from the 90s will still work in 10 years either. Both those mediums have an expiration date usually, Discrot is a thing and Cartridges can go bad as well.

You can still download your purchases on the Wii and DSi nowadays, even if those stores have been down for years. Plus, should Nintendo in the future decide to shut the store and the servers down, they will do so only after an announciation, which will give you time to make sure your GCKs are downloaded to your Switch 2 or SD Express card. You will be able to play those for forever technically, since the GKCs don't require an internet connection, as long as the data is downloaded.

Yeah, some things we buy decay over time. Thats ok. Thats no ones fault. Its not really a widespread issue at the moment though. Sure Game Gears, Atari Jaguar CDs and other badly made consoles stop working, but that has been an issue for those devices for like 25 years(maybe even longer)at this point. 

The point I am raising is that old tech has its own set of problems. Parts are becoming harder and harder to find - especially if you want to preserve rather than upgrade with modern tech. Many of us were kids when we owned these systems. We were not museum curators, so did not look after them in the way we should have. It means that many of these systems and their games don't work anymore. It is not a justification for Sony's action - but we need some perspective when we compare physical media of the past to the present situation.

For me the main problem today is preservation and ownership. Sony's move does not give me confidence about either of these issues. I cannot trust Sony to 'preserve' - given their practices. I also would not trust that I will indefinitely 'own' the digital games I purchase.

I fully support game preservation via emulation for these reasons. There will be a day when my NES cartridge will be nothing but an artifact to display. No real use value. The game it contained will still be available to me, albeit via another form factor and playable on an a different system - and that's what matters to me.

The big reason people dislike them is because 10-15 years down the line, Nintendo might not have the download options ect.
Meaning the key card becomes juist plastic junk, at that point.

However the counter argument is this:  https://www.youtube.com/watch?v=wY16S5x3dHc

The same thing happens with games that are on the Cartridge as well.
New firmware makes it so, you cannot play a offline game, if your system knows that there are patches to it, without updates.
Essentially bricking the game, if you cannot download the patch (which 20years down the line, you might not be able too).

*edit:
This is bad for game preservation.
Afaik, Xbox does the same thing.... I think only the PS5 of the 3 consoles actually values allowing you to play a game, where you have the intire game on disc, if in future say there is no way to download patches ect.