I have owned 2 bakeries and my biggest request was for lowering the fat/oil content and keeping a good flavor profile and texture.
I have had a lot of luck with unsweetened applesauce, only replace half of the fat/oil and equal amounts. I have used persimmons (puree’d), prunes, almost any dense fruit can be used. I also used to replace the sugar in recipes by using half the amount of sugar replaced with unsweetened applesauce or dense fruit and the other half with Fruitcase. If I was replacing 3 cups of sugar, I would use 1 1/2 cup of fruit and 1 cup of fruitcose. Fruitcose is a natural sugar derived from fruit and it is very sweet. Most diabetics know how to use it in their diets.