You can duel, you can build decks, you can relive the story, you can take your decks online, all of the things that SHOULD be in the game are there for you to enjoy
While you can tune engines to draw extra cards and control the game, some tactics are simply more consistent (bunnies can easily overwhelm an opponent, for example, thanks in part to the new Offspring mechanic)
All Will be One is out next week!
However, its two-week free trial is extremely generous
Articuno ex is among these powerful basic Pokmon, but it does not have nearly the meta impact of Pikachu ex or Mewtwo ex, as those two Pokmon deal more damage and can consistently accelerate energy to their board while not relying on luck-based mechanics like the coin flips from Misty