Much of the initial design come from improving the language grammar and syntax. That limited improvement didn't last long, but it was an initial motivator (Walter being a compiler writer and C++ being horrible language to parse).

The D community has greatly pushed D away from this initial improvement. In C++ there is a separation of the developer tools and the library writer tools. I think that separation still exists in D, but it is in an area even library writers don't/can't reach for in C++.

Ultimately D doesn't force a fundamental change, but as one learns to use the language, the result is a fundamental change.