Ay dodged it point blank. Thats not prep time. Thats godly speed. There's no way you can refute that.To be fair, Nagato and Ay both would have lost eventually. Ay needed a decent amount of prep time and prior knowledge of the technique and warning sighs, and Nagato only survived because he was an Edo. Nagato's arms and legs were still severed before he could dispel it.
If you aren't someone with a powerful absorption technique, or top 3 speed in the world, you're not surviving Amaterasu.
Amaterasu is a dangerous tech if it isnt getting sealed, dodged, repelled or b!tch slapped