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You mean besides forcing you to rely on an internet connection to download a game that you own in a physical cart, pricing them just as expensive as if it was on a real cart with actual storage capacity despite being much cheaper for the publisher to manufacture, having to pray for the publisher to not remove your game from the eShop at any point and having to insert the cart every time you want to play despite the game being downloaded on your console? Yeah, I can't think any reason as to why they are so controversial.
The point about removing X game from the eShop is not talked enough. GKC defenders will say that even if the eShop stops selling games, you'll be able to download the games you already own. Well, what happens with GKCs if the product itself is removed from the eShop for whathever reason? It's not unheard of and even Nintendo has pulled that off sometimes (Mario Bros. 35 not too long ago for example) and if it happens you will most likely end up with a nice and useless GKC that will show up on your menu when inserted, but won't be able to download its game.
Really, GKCs are the worst solution ever to the storage problem on handheld devices. Most publishers (even Nintendo) could have easily used Switch 1 cards of high capacities (in 2026 they are probably not very expensive) instead of empty cards. If loading speeds are the issue, just make the console install the game internally FROM THE CARD. That way you bypass the need of an internet connection and an external source. As for very large games like FF VII Remake, for the love of God: compress the fucking game. Why the hell does that game weigh almost the same as the PC/PS5 version? It has plenty of pre-rendered video cutscenes (some are disguised very well as real time in-engine) that, if compressed, could probably put the file size in the 64 GB territory.
If we think about all of this a little bit, we realize that there are actual solutions that would allow publishers to offer a not that expensive physical solution, and that the only reason GKCs exist is publishers (and Nintendo's) greed. By using GKCs, they reduce the manufacturing costs significantly (how much storage does a GKC hold? 1GB?), they don't have to put up the effort to actually compress and optimize their games to fit the physical media and they can charge exactly the same price as if they were actually offering a real physical game. In exchange, the customer gets all the negatives that come with it and not a single positive thing.
