Here's why:
* Power is subjective: "Most powerful" is a relative term. It depends on the context, the deck, and the situation.
* Limited uses: While Wiraqocha Rasca is a strong card with powerful effects, it has significant limitations. It requires specific summoning conditions, can be easily destroyed by powerful monster effects, and is vulnerable to spell and trap cards.
* Other powerful cards: There are many other cards in Yugioh that are considered more powerful or have broader applications than Wiraqocha Rasca, such as:
* "Chaos Emperor Dragon - Envoy of the End": A powerful boss monster with a devastating effect that can destroy all monsters on the field.
* "Dark Armed Dragon": A strong monster with a powerful effect that can banish cards from the graveyard.
* "Pot of Greed": A simple but incredibly powerful spell card that lets you draw two extra cards.
* "Harpie's Feather Duster": A powerful trap card that destroys all spell and trap cards on the field.
The bottom line: While "Earthbound Immortal Wiraqocha Rasca" is a formidable card, it's not universally considered the most powerful in the Yugioh game. Power is relative, and many other cards have the potential to be more dominant depending on the situation.