I'm not saying that D is defined by that. I'm simply saying that if you're comparing to C or C++, you are talking about use cases that are defined by performance and/or memory management (or else, they are being used for legacy reasons). If you have a green field project that doesn't have massive performance concerns, and doesn't have to be specifically in C or C++ for other reasons (toolchain availability, available developer resources, etc), you probably aren't using C or C++.
Some people would argue that you can use D for equally high performance things to C++, and make sure you use the GC very selectively, etc. However, you don't appear to be making that argument. If you aren't, then there's just no real point comparing C++ and D. If you don't have any of those requirements, and you are ok with obscurity, you have much stiffer competition from many other languages like Haskell, Kotlin, etc.
Some people would argue that you can use D for equally high performance things to C++, and make sure you use the GC very selectively, etc. However, you don't appear to be making that argument. If you aren't, then there's just no real point comparing C++ and D. If you don't have any of those requirements, and you are ok with obscurity, you have much stiffer competition from many other languages like Haskell, Kotlin, etc.