I agree with you about preferring real sugar instead of a substitute, up to a point. One teaspoon of sugar contains 4 grams of carbs, an amount I can deal with blood-sugar wise. Amounts greater than start to give me more trouble. A teaspoon a sugar on a serving of tart berries is a treat for me that I can handle.
Did you know that table sugar, sucrose, is actually half glucose and half fructose? Did you also know that fructose takes an entirely separate metabolic pathway in the body than glucose? Fructose is handled by the liver.
The problem with sugar as a carb is that it doesn’t carry any nutritional payload. People who consume a large percentage of their daily calories as highly processed carbohydrates loaded with sugar are displacing dietary items that provide a much wider nutritional benefit.
Sorry I can’t cite any studies off the top of my head so I’ll stop here before I move on to more opinions.