You cannot copyright a vague idea. No matter how much Nintendo might want to.
The game is basically just magic animals in the world that you can capture and do things with. It’s literally every JRPG ever. It’s just mounts with extra features.
Nintendo are suing them, but Nintendo sue everyone.
The Japanese copyright courts are stupid, it doesn’t matter how clearly something isn’t a case, it still goes to trial if one of the parties is big and important enough. They don’t seem to have proper separation of law and government. So political bigwigs can get involved.
Even my parents know what blue sky is. This is from the people that were concerned that my emails wouldn’t be able to find me when I moved house. Because “how would they know which house to go to now?”
If even they’ve heard of the platform, it’s reached the mass market.
People are constantly say the same thing about Steam yet I don’t see any kind of pushback against everyone using that platform. Yeah it’ll suck when it eventually happens but that doesn’t mean I should have to use a more irritating service in the interim.
There’s literally no reason not to do that. The game has long since made money and keeping it out of public ownership is now not doing anyone any favors.
It doesn’t need to be anything complicated. If you just re-upload the original code to a new location, and then Nintendo has to start the entire process of tracking the uploader down in order to threaten them.
Ironically for a video games company Nintendo don’t really seem to quite understand how the modern world works.