Mystic Forge Combo is almost entirely colorless artifacts and lands, so Consign to Memory is a premium answer that counters their colorless spells (Kozilek's Command, Giant's Boulder, Grim Monolith) and triggered abilities for cheap. Swords to Plowshares has few legal targets since their deck is nearly creatureless outside of rare artifact creatures, so it comes out. Back to Basics is risky against a deck running many utility nonbasics we rely on ourselves, and they can sequence around it with Urza's Tower/Workshop/Saga, so it's cut for Crucible of Worlds, which helps us out-grind their Wasteland-adjacent land disruption and rebuild lands including fetches.