What big surprise? You yourself pointed out the exact same thing happened last season and if you think so little of the Freys, what difference does it make to you that she used the same or similar trick to kill them.
The surprise is that no one saw it coming, that's quite obvious.
You're saying just the freys and I'm saying Jamie was still on site with Arya. Are you now saying Jamies troops are worthless as well?
Her path to and on the grounds wasn't shown,,,ehhh, so what?
Let's assume I entertain the idea of Arya sneaking around a castle without problems . I've already said Arya doing that is bullshit given her age and experience. It's not a question of what happened or how it is written. I'm saying the writers did a poor job of showing her growing overtime and I don't see her being flawless killer.if you can't give me a time frame of how long she was training, why would my views change.
She's was an advanced student and has graduated. Training is done. Not all students excel in the same manner. So they didn't spend more seasons on her training,,,ehhh, who cares? So far she's made two flawless kills (and probably more to go), so questioning her being an assassin is silly.
By the way outside of Jamies comments what makes them incompetent. Trick or not they were good enough to beat Rob Stark during the red wedding. Granted the troops were probably mostly drunk, but they did execute the plan.
The hostage situation spoke for itself. It was Tywin Lannister that planned the Red Wedding. House Frey was merely hired help to do a simple job on orders from Tywin to end the war. House Frey wasn't the brains behind that operation and couldn't even prevent the Brotherhood without Banners from constantly raiding their supply chains, much less hold on to Riverrun. A competent Lord keeps the Houses within the Riverlands united rather than have them oppose and raid.