While Ay was capable of keeping up with KCM Naruto.
Itachi was able to fight on par with him, it wasn't until Killer Bee came in with Samehada that Itachi backed off in the Taijutsu scuffle.
Madara Tsukuyomi'd Ay easily, let's not forget that Madara isn't much of a genjutsu fighter to begin with.
Itachi can beat all non Uchihas (Sage's family and Indra don't fall under this) excluding Hashi and pain's 6 paths because of his genjutsu.
A only got caught in a genjutsu thanks to the fact that he had 5 Susano'o clones and Tsunade to look out for. Even then one of those clonesYou must be registered for see links. None of those factors exist here. And since A has knowledge of Itachi's Mangekyo Techniques he will use his V2 Raiton cloak, which erase any chances of Itachi catching him with Amaterasu, Susano'o, or anything really.
On the other hand Itachi needs to keep up a Susano'o higher than Ribcage if he wants to survive, which will do a number on his bad stamina. This means he'll eventually wear himself out and A can come in for the kill. A can keep up his cloak much longer than Itachi can use his Susano'o/Amaterasu.
Ay is reckless, plain and simple. He's hot-headed, impatient, and careless, whereas Itachi is calm, patient, and careful. Tbh Itachi could throw up his Genjutsu before the fight even starts, not to mention he could use KA too if he wanted, but that's just overkill.
How is he gonna anticipate amaterasu if he isn't looking at itachis eyes? He loses either way it's not debatable.