Uncounterable is a nice perk although not that frequently relevant
With the debut of the new "Space-Time Shakedown" set, several ultra-powerful decks have begun to emerge (read more about the best Pokemon TCG Pocket decks here), but a card like Arceus coming into the game could change that drastically
They often let other merfolk be played from the library, create merfolk tokens when their allies enter the battlefield, or have ways to protect each other that quickly add up
But it's more useful than other graveyard effects like persist and undying in a self-mill build because those effects trigger on creature death, while unearth works as long as the card is in the graveyard
The update streamlines the booster pack system, brings all the cool new EX Pokmon with special abilities under one roof, and provides new gameplay opportunities for players
The game play mechanics aren't much different though, as it still follows the exact same card game