Izzet Spellementals grows Hearth Elemental and Eddymurk Crab as it chains cantrips together, so removal that answers a specific evasive or growing threat is much better than our slower mana sinks. Erode and Sheltered by Ghosts each remove their best threat regardless of size, while Soul-Guide Lantern can strip a card from their graveyard to slow Eddymurk Crab's cost reduction from instants and sorceries piling up. We already have plenty of exile-based removal in Seam Rip for cheap permanents, so trimming a couple copies for more universal answers to their bigger threats is worth it since Seam Rip whiffs on their 5/5s.

UR Aggro wants to build early board presence with efficient creatures, so we need cheap, efficient answers rather than symmetric value cards. Erode and Sheltered by Ghosts both remove their key threats outright at low mana cost, letting us keep pace with their tempo plan instead of falling behind on board. Cutting the slower Multiversal Passage and Ouroboroid tightens the curve and gets us proactive removal online faster, since this matchup is decided by who controls the board in the first few turns.

Azorius Tempo leans on evasive threats like Aang, Swift Savior and Aven Interrupter backed by cheap counterspells and removal (Get Lost, No More Lies, Avatar's Wrath), so we want efficient answers to their key flyers rather than mana sinks that do nothing under pressure. Erode and Sheltered by Ghosts both handle their evasive threats outright and dodge their countermagic suite by being cheap, low-commitment answers. Trimming Ouroboroid and Multiversal Passage keeps our curve tight so we can keep applying pressure while removing their best blockers or attackers as needed.