The SAD is high fat and high carb. The lowering of either macro nutrient is an improvement. Low fat high carb diets have improved the health of many people because it reduces sugar consumption and focuses on real foods. Alternatively, a “keto” diet even if it’s not low enough in carbs to result in a state of ketosis, is still a vast improvement over the SAD.
Whether a newbie is considering a keto diet, Ornish, Atkins, vegan, Paleo, raw, DASH, TLC, Mediterranean, all are an improvement over the typical diet they’re likely eating. No warning is necessary. And perfect execution is not needed. Just do it.