Izzet Delver is an almost entirely blue-and-red deck where Pyroblast and Red Elemental Blast can counter Murktide Regent, Brainstorm, Ponder, Daze, or Force of Will, or destroy a resolved blue permanent; despite our thin red sources (Volcanic Island, Mountain, fetches), even a couple live copies swing key turns against their tempo plan. Back to Basics is risky since we don't want to lock our own thin red splash out of mana, and Counterbalance is weaker against their varied one- and two-mana suite (Lightning Bolt, Daze, Ponder) that doesn't line up on a single mana value. We keep our own countermagic and removal as the primary interaction plan alongside the Blasts.