They all may have excellent C compatibility, but this is not the point. The point is that without C compatibility C++ could be smaller and simpler, and yet still meeting the same goals and covering the same use cases. Objective C has Smalltalkish object system glued to C base. Fundamental C++ techniques like RAII not possible there. D has GC. C# runs in a VM. I would not call a language with any of those features very similar to C++.

OTOH if not for C compatibility we would not have this discussion, since we would most likely never heard of C++.