This year's Halloween was the first in a few years that Ariana hasn't gone all out for. It was a day her and Mac used to have fun with, and it's no question that Ari wasn't in the headspace for it this year.
But! Fans aren't totally left without an 'Ariana Grande costume', as Kourtney Kardashian literally went as Ariana Grande for her second Halloween costume.
Sources: 1, 2