Izzet Delver leans heavily on Mishra's Bauble and colorless triggered abilities, so Consign to Memory picks those off cleanly while also countering triggered abilities from Cori-Steel Cutter's Monk tokens. Blue Elemental Blast is a great value swap that can destroy a resolved Dragon's Rage Channeler, or counter a red spell like Lightning Bolt outright. Wrath of the Skies is too slow against a deck that can kill quickly with a grown Murktide Regent or Cori-Steel Cutter equipped creature well before X gets big enough to matter. Spell Pierce is redundant with our own counter suite and less impactful since they're also on Force of Will and Daze to protect their spells.