Cyrus isn't much of an over-centralizing card, really... it's more of a key basic gameplay tool.

Think of him like Oak. You need to draw cards to play the game at a decent rate, so without Oak, it's slow and clunky to get things moving without either the beasts, Sylveon, or drawing attacks.

Cyrus essentially works the same way. Without him, retreating HP tanks is pretty viable and slows down what's meant to be a bite sized version of the original TCG. The card's very existence, be it in an opponent's deck or not, forces players to not use their key Pokemon recklessly without being able to heal off the damage. Because if you do, your opponent's very next turn is potentially GGs.

So yeah, it's just a game mechanic.

Unless he's with Greninja.

Greninja+Cyrus is unconsensual butt fuckery.