The ability to skip the natural window of interaction for creatures that summoning sickness creates on a creature that cannot be blocked under most circumstances is inherently powerful
Spell/Trap destruction is strong in this meta where Continuous cards are involved in combos
Guaranteed Super Rare or Legendary Some meters promise a high-tier card after enough pack openings
In every zone other than the stack, Twice Upon a Time uses only its non-Adventure characteristics, and you ignore its alternative characteristics in those cases
Basically, if youre going up against an opponent who uses any attribute other than Dark in their deck, this Monster gives you a huge advantage
These are: Abuelo's Awakening Cori-Steel Cutter Heartfire Hero Hopeless Nightmare Monstrous Rage Up the Beanstalk This Town Ain't Big Enough For better or for worse, these bans make sense for different reasons, and the general idea from WotC was to make Standard slow down a bit while reducing the power of problematic decks