Back when home brew was a baby the sugar bogeyman was born. There were many reasons and some are still applicable. To cut a long story short many of those off tastes, generally bucketed as "home brew" were put down to a single culprit..sugar. These early brewers were on the whole, extract brewers..I figure that even today there is more beer made in kits in Australia than mashed. The real problem was a witches cauldron of bad shirts..old extract, yeast past its best, cheesy hops....
Malt extract has low levels of FAN..free amino nitrogen, an essential beer yeast nutrient, old extract starts to oxidise and the FAN levels may drop as well so we start off with not the most viable yeast in a smaller than ideal pitch rate into a poor medium that at least has a fair whack of sucrose, the yeast lags too long, does not reproduce enough of its already paltry numbers, we get lots of fermentation problems and the off flavours from acetaldehyde to diacetyl and thats without an infection, sugar is called white death and things move on, the extract is fresh, the yeast viable, fermentation is done at lower temperatures the sun sets and rises etc but no-one forgets the scapegoat..sugar.
The "accepted" knowledge seems to be that the use of sucrose at the level that kit manufactures say to use will impart a cidery (?) taste to your beer. You can certainly get acetaldehyde (green apple) from a number of sources, mainly to do with fermentation but I have yet, over the last 6 or 7 years to be convinced that there is something specific about sucrose as opposed to maltose, dextrose, fructose and so on that will produce this "cidery taste"...the cidery taste is not a product of sucrose, it is a result of process.
K