Winterfell - S8-E1
Visible crew/equipment: After Sansa tells young Ned Umber to hurry back to Last Hearth and bring his people to Winterfell, when Jon tells Maester Wolkan to send ravens to the Night's Watch, in the next shot of Wolkan the chalk T-mark can be seen on the stone floor in front of his feet (it's not the stone's edges or cracks). (00:11:20)
Visible crew/equipment: When Bran joins Tyrion and the others at the small council meeting, Bran begins by saying that they appear to be missing a Master of Whisperers, then just as he says, "And a Master of Laws," the boom mic can be seen dipping into view over Bran, at the top of the screen (visible on Hulu). (01:11:00)
Visible crew/equipment: At the Wildling camp, before Jon and Ygritte go into the cave, there is a modern building, and clutter visible in the distance.
Answer: Daenerys and her allies don't just want to kill Cersei, they want to claim King's Landing and free her people from Cersei's grip. The problem is the people of Essos viewed Daenerys as a liberator but the people of Westeros view her as an outsider and usurper. They would never follow Daenerys if she had Cersei assassinated. That is Daenerys' dilemma, she certainly has the ability to wipe Cersei out and obliterate her armies but doing so would make her a tyrant. Which as it turns out is exactly what happens.
BaconIsMyBFF
But no-one has to know that Cersei was assassinated. Arya has the ability to impersonate anyone she kills, so she could pretend to be Cersei afterwards and profess to the citizens of King's Landing that she has yielded the throne to Danaerys and that she is going into exile.
Phaneron ★
That plan would be incredibly suspicious. Knowing what they know of Cersei it is highly unlikely the people of King's Landing would believe that she would accept defeat so easily and then voluntarily exile herself, never to be heard from again. In order for that to work, all of Cersei's advisers and closest allies would have to be similarly eliminated, or they would have to be on board with the exile plan. If they are all killed it sort of makes it obvious that something is amiss. There's no way they would be fooled by Cersei suddenly doing a 180 and completely changing her personality by accepting defeat without a fight. If any part of this plan goes wrong then Daenerys would look worse than just an assassin, she would also be deceitful to the people she hopes will willingly accept her rule.
BaconIsMyBFF