Lipolysis is the inherit, main metabolical function of our liver and muscle cells. We cannot make use of monosaccharids without "switching" our cells into another mode. This is done by the pancreas secreting a hormone, insulin, into our blood stream; the hormone signals to our cells to stop burning fat and just store it instead, in order to focus on processing the sugar in the blood to prevent a sugar coma. Sugar is in essence a poison in the blood stream, and a too high presence of it will end your life at shortest within minutes. Also, we cannot store sugar for any mentionable duration of time - it's not a long-term energy source the way fat is. This is also the case for almost all other animals on the planet, mammals in particular. If the roles of sugar and fat would be reversed - sugar being storable, lipolysis needing to be acquired through switching of cell function - we could come to a different conclusion.
Today we have empirical evidence, through years of study of people living on rigorous LCHF diets, that the human body does not require a single gram of sugar a day to function; it can slowly adapt and switch entirely, both brain, core and limbs, into being solely a fat- and protein-consuming machine. We can from this perspective consider sugars as being available as an alternate form of energy that we can process by secondary function, at a cost - the cost of insulin in our blood stream, and all the problems that can come with the production of such (various cardiovascular diseases have been linked to this, as well as the cases of insulin resistance and lack of insulin production from the pancreas from being "burnt out" being the two major problems).
How would our metabolism have to be different for you to come to a different conclusion?
(I just want to know, how strong your statement is.)