Perhaps the balance of too many variegated plants has been tipped beyond the point of distraction, but I suspect that jarring foliage contrasts are the least of problems a design purist would diagnose in this garden. In any case, my eye is easily pleased, regardless that cardinal rules of landscape design might be trampled into dust.
I expect that, with the exception of hostas, few gardeners share my overzealous enthusiasm for variegated foliage. Perhaps there is a simple explanation, that the simple minded gardener is attracted to any plant with huge or variegated foliage, while the more sophisticated eye is drawn to more subtle contrasts. Guilty, I am.
There is no more elaborate explanation to the design of this garden then plant what I like, and try to make the best of it. If there is no better place for the variegated Cornelian cherry (Cornus mas ‘Variegata’, above) than immediately beside a variegated yellowtwig dogwood (Cornus sericea ‘Silver and Gold’), so be it, though this is done with at least some measure of reluctance. But, no apologies.