The big 6 is an outdated concept. It made sense back in 2022 or 2023 when Pogačar was still beatable even on races that suit him and Van Aert and Roglič were still in their prime, Right now, it makes more sense to talk about tiers.
Tier 1: Pogačar
Tier 2: Vingegaard, Van der Poel, Evenepoel...