I think it is a combination of several things. For one thing, the fabrics today are so much richer and more vibrant looking than fabrics were 20+ yrs ago. So you can take a traditional design and really make it spectacular just by using today's fabrics. Also, with it now being easier to buy acrylic templates and have the ability to print off your own foundation papers, more people are willing to make quilts that have "weid" angles and sharp points. This makes it fun to take a traditional design, such as a churn dash, and turn it in to something really jazzy.
I think one of the terms for modern quilts is Wonky. Everything is Wonky. Also, in a lot of the modern quilts they are using more neutrals, traditional like white and not so traditional like greys to offset a specific pattern.