Really depends on the meta environment of the tournament (IE what the popular decks/mechanics are right now. That fluctuated as cards enter/leave the format. At least, in MTG that's how it flows. Yugioh may be different. I do not know if they have set rotation or banlists in certain formats) "Powerful cards" are often prepared for and countered, so it's not always a guarantee.
Might also not fit the theme or mechanic yuo've built a deck around, so may not be something you play. Or on the flip side, something you specifically build a new deck around.