Quilting does not have to be dense to be beautiful.
Having said that, though, there are other factors that contribute to stiffness; it's not just a matter of the density of the quilting. The type of batting used makes a huge difference in how soft a quilt ends up. For example, a quilt with the same amount of quilting done using Warm and Natural batting will not be as soft as one done with Hobbs PolyDown batting. Also, the type of thread used can make a ***huge*** difference. Dense quilting done with a fine polyester thread in top and bobbin (such as Bottom Line) will not be anywhere as stiff as dense quilting done with a relatively heavy cotton thread in top and bobbin (such as King Tut).
Balancing all 3 factors in a longarmed quilt will give you the result you are looking for.