Q. What foundation shrub would do well in shade?
Yews are about the best shrub for dense shade. You can have the Cornus kousa tree thinned out and cut back the yew significantly. It should send out new shoots and grow satisfactorily. If you are not satisfied with this solution, you can try Acuba japonica, oakleaf hydrangea, Japanese holly, or herbaceous perennials that grow in dense shade.