Izzet Affinity doesn't run mainboard countermagic, but Defense Grid is still valuable here because it blanks their sideboarded Force of Will and Consign to Memory on your turn, letting your Aluren and Show and Tell resolve safely once the games go longer and they bring in interaction. Omniscience is far too slow against a deck that can assemble Kappa Cannoneer or Emry, Lurker of the Loch kills quickly, so both copies come out. Acererak the Archlich is also a weak top-end creature here since it doesn't interact with their artifact-based plan and is cut for a faster, more consistent combo configuration.