It's part of a larger systemic problem with the way they're playing Arya's story. They're really dismantling much of the bite in her transformation, and it's disheartening. They've nailed many storylines and then nailed Arya's story in season 1, but season 2 is all sorts of going wrong for what they're doing and taking out of her journey.
The Ticker scene as it occurs in the books is such a perfect payoff, and as any good show or book knows, letting a character actually build to a moment makes a payoff infinitely more satisfying. Let alone how Arya did it - which was all sorts of memorable in its own right. And it just so happens it was a big part of Arya's character growth.
Now what are they going to throw in there? A random kill? Will Arya get her timeless lines of revenge? Will it show the monster she has become in the same light? I think not.
The show is quite good but when it's wrong, it's wrong.
Then you have a shit memory. Blame yourself or God.