The whole comment about the Seven Rainbow Crystal monsters being to modern really isn't a plot hole. It has been shown in multiple adaptations that the Silver Millennium and Golden Kingdom were far more technologically advanced and magically advanced then the modern era so they could very well have arcades etc.
It’s not a plot hole because it’s not really a hole in the plot. It’s an anachronism at most. Not every nitpicky thing is an issue with the plot hole. I still think its ludicrious for the moon to have arcade games circa 992 AD but what can ya do?
Now the show stating the silver crystal shattered into the 7 rainbow crystals after Queen Serenity trapped them in the silver crystal but then we find out she sealed EVERYONE into the silver crystal. That’s arguably a plot hole or a continuity error at least