As the game evolved, set symbols became standard, allowing players and collectors to quickly identify which expansion a card belonged to
Indecisive Parody: The series is this to Duel Monsters
It was extremely popular and controversial
The real value is when you cast it for its disturb cost, however, giving you a pseudo-Lier, Disciple of the Drowned effect
While you do need to make sure you have a reasonable number of untapped lands in your deck, between dual lands and basic lands this shouldn't be a problem
And, just like the Koraidon card, Miraidon here is in the same pose as seen in the Full Art Miraidon card (which also happens to be one of the more valuable cards in the Scarlet and Violet TCG)