Dimir Control has very little in the way of artifacts or enchantments worth targeting with Deglamer beyond incidental value, so this swap is modest, but Thermokarst is weak here since they run few basics to blow up and land destruction doesn't slow a deck full of card draw and counterspells. Your plan is to grind through Counterspell and removal with card advantage engines like Mwonvuli Acid-Moss and Boarding Party's cascade, forcing them to answer multiple threats. Keep Wild Growth and Utopia Sprawl online to play around counterspells by deploying bigger threats they can't afford to leave unanswered. This is a close matchup where sideboarding is light since your mainboard already does most of the work.