Doomsday is a combo deck that digs with cantrips like Brainstorm and Ponder to set up its Doomsday pile, then wins with Thassa's Oracle. Consign to Memory can't counter those blue cantrips, since it only hits triggered abilities and colorless spells. It is still live here because it can counter Thassa's Oracle's enter-the-battlefield trigger, which is their win condition, and it can also stop colorless spells like Lotus Petal and Lion's Eye Diamond. Tormod's Crypt is a proactive answer that can strip their graveyard in response to Doomsday, which searches the graveyard as well as the library for its five-card pile. Eldrazi Confluence is too slow and reactive against a deck that can combo off quickly once Doomsday resolves, and Sink into Stupor only delays a spell or permanent rather than answering it, so both are trimmed for proactive disruption.