Izzet Delver plays colorless cantrips like Mishra's Bauble and leans on red removal (Lightning Bolt) and red threats, so Consign to Memory strips their colorless utility and Hydroblast answers their red cards: it can counter a red spell like Lightning Bolt or Unholy Heat, or destroy a red permanent like Dragon's Rage Channeler or Cori-Steel Cutter. Hydroblast can't touch Murktide Regent, which is blue. Shuko doesn't meaningfully help race a deck with efficient removal and burn, and Orim's Chant is too narrow against a deck with free counters like Daze and Force of Will already protecting their plan. Keep Swords to Plowshares in to answer Murktide Regent or Dragon's Rage Channeler quickly before they grow out of range.