So...why didn't Dany do that to Euron's fleet last week?

Fire and blood

Thank you! That's what I said! She was flying straight at them--why didn't she yell Dracarys?

Agreed - they shot down one dragon and almost got her as well. In this episode, a few ships took a few shots and then stopped shooting - and there weren't like a hundred spears in the sky like the first time - for no reason at all other than shitty writing.

First they make those scorpions look like the true anti-dragon weapon, and then they turn them into children's toys just for the sake of the narrative where Dany burns the whole city to the ground.

She took them by surprised. The first time they ambushed her.

This time she came from straight above where the arrows couldn’t aim. She also did a lot of side attacks that made those arrows pointless.

Because last week was a surprise attack. Her other dragon was hit first. She had to reassess, not charge immediately against the giant crossbows like the Dothraki charging into the night against the Army of the Dead.

The Iron Fleet was immobile this time -- you notice their sails were down and the wind was barely blowing -- they couldn't have maneuvered in time.

I said the same thing! "Damn why didn't she do that last week?"

Dany rode towards them from the direction of the sun which meant that Euron's people couldn't see the dragon clearly because of the sun's blinding glare.