Aura of Silence taxes their enchantment-heavy spells and can sacrifice itself to destroy Opalescence, Parallax Wave, or an animated enchantment, while Enlightened Tutor finds it precisely when needed. Thermokarst comes out since it is too slow against a deck trying to combo off with Replenish; Naturalize is cut because Aura of Silence is a comparable answer that also taxes their spells. Keep Wasteland and Rishadan Port to attack their Ancient Tomb-fueled mana.

Cursed Totem does not stop Stifle or counterspells, but it does shut off any activated ability a creature might need, which is low-impact here since their core engine is cast triggers and instants, not activated abilities, so this is a marginal inclusion at best. Your 2 maindeck Naturalize already give you clean answers to Phyrexian Dreadnought, an artifact creature, so no further anti-artifact tech is needed from the sideboard. Thermokarst comes out since this is a 17-land mono-Island deck with little land disruption upside, and Wasteland/Rishadan Port already punish any nonbasic lands they run. Focus on deploying threats like Treetop Village and Mishra's Factory, which dodge their countermagic by not being spells, and race before the Dreadnought combo assembles.

This Gruul Goblins list has essentially no artifact or enchantment permanents listed, making the extra Naturalize copies low-impact unless they bring in something like Cursed Totem or an artifact from their own sideboard; hold these mainly as flexible instant-speed interaction rather than a dedicated answer. Cursed Totem shuts off Goblin Sharpshooter's and Goblin Tinkerer's activated abilities, which can matter if they win the race through repeated pings. Sylvan Library's life payments are risky against this aggressive creature swarm, so trim one copy, along with a Thermokarst and a Winter's Grasp since they have a low land count (their lands are mostly utility, not a liability to destroy) and land destruction is too slow against their fast curve. Swords to Plowshares and Mishra's Factory remain your best tools to control the board.