Drop biscuits are a little crumbly by nature, but they can be dry if they are overbaked or if too much flour is used. I find that measuring the flour by spooning it into the measuring cup ensures that I do not compact the flour and use too much. (You can also use a scale to measure your flour. It varies between brands, but the weight of 2 cups of all-purpose flour of the two brands that I use is about 250 grams of flour.)