WU plays Stifle, Teferi, and a battery of countermagic, so Force of Negation is valuable for answering their noncreature spells (Teferi, Time Raveler, Swords to Plowshares, Stifle, Force of Will, Consign to Memory). It is only free when it's not our turn, so on their turn we can exile a blue card to counter something like Teferi at no mana cost. On our own Doomsday turn it has to be hard-cast for {1}{U}{U}, and it can't touch creature spells such as Tamiyo, Quantum Riddler, or Phelia. Fatal Push has fewer good targets here: it can't hit Quantum Riddler (mana value 5) or Teferi, and Tamiyo becomes a planeswalker once flipped, though it still handles Phelia and an unflipped Tamiyo, so we trim it. Brazen Borrower's Adventure bounces a problematic Tamiyo or Teferi, Time Raveler, buying tempo, and the flash body can block their fliers (it can only block creatures with flying). Daze gets cut some since it taxes us into their Force of Will/Daze mirror poorly once they're playing around it.