Do you not know, Lord of Sharks, that in order to disable the AT... well...
It turns out Xenahort actually managed to capture Sakurai's Nobody, and is holding him hostage over Sakurai's refusal to send Xenahort an invite to Smash. Especially when Sakurai sent an invite to a pretty white-haired boi who Xenahort somehow missed when his own nobody dealt with Sora. So, he used Sakurai's Nobody to lock the ATs disabled in place not just so he could prep his attack on Fodlan, but also so that he could tie Sakurai's Nobody to a Meteor and "accidentally" drop the spell somewhere in Duckburg. Why Duckburg? Well, not only does several of Mickey's allies - well, a version of their allies anyway - live there, but also something about that world's Keyhole being connected to a galaxy far far away for some reason and Xenahort just naturally could connect to a certain force for some bull**** reason...
Leading Sephiroth and Darth Vader on a collision course in Duckburg. So yeah, in order to disable the AT, you'd have to fight both Sephiroth and Vader in Duckburg before the Meteor spell blows up the place faster than Sonic - who's also trapped there for some reason - can say "BLOWS UP?!"
And even then, disabling the AT is not only part of Xenahort's plan somehow. this is also part 3 / 16 of Xenahort's Completely-Foolproof-and-not-at-all-Idiotic-Plan (and yes, I'll complete the entire thing, just to discover there's a part XVII: Chain of Deluxe 358 Days fawning over Disneyworld).
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Previous parts of this ****post that could actually be Kingdom Hearts V.)