When I was a pastry chef, I frequently received requests from customers who planned to order my desserts for a special occasion, but wanted me to adjust the recipe to make them sugar-free.
I always said no. It's not that I wasn't sympathetic to the dietary requirements of diabetics (or people trying to lose weight), or that I was opposed to sugar substitutes or artificial sweeteners on health grounds. I didn't do it because changing the recipes would have required a lot of experimentation to make them as delicious as they were when using sugar.
It seems obvious that you can't just substitute equal measurements of sugar substitute or artificial sweetener for sugar - they are much more intense and a little goes a long way. Sugar isn't used only for sweetness in desserts - it's essential for texture. It gives tenderness to cakes, breads and pastry doughs, and through caramelisation, helps them bake to an appetising brown colour. With sorbets, ice creams and other frozen desserts, you need the right amount of sugar, because too much will prevent them from freezing hard, while too little will make them grainy. Without sugar, whipped foams and emulsions - such as meringue and sabayon - are less stable, and have more risk of collapsing.
Using sugar substitutes is less tricky in savoury dishes, where sugar is used in small enough quantities that it doesn't affect the texture. But with sweet dishes, it's tricky. If you want to try to adapt a recipe to make it sugar-free, change your expectations, because it won't be the same. It's probably better to let the experts do the experimenting, and buy a book dedicated to sugar-free desserts. Or, if your diet allows it, and you have enough self-control, eat just a mouthful of a regular dessert, rather than a whole piece.