With good/better I mean that it seem simpler yet it has all the good stuff within C/C++
It doesn't. It has many of the good features of C++. But not all. It is missing the single biggest reason why people write C++ code: backwards compatibility. Most people do not write C++ code because it's the best language. They do it because they've got a large code base written in C or C++, and they need their code to be compatible with that. Or they're using libraries and APIs written for those languages.
If you're willing to give up on C/C++ compatibility, then yes, D is a much nicer language than C++. But so is C#, Python, Ruby, Haskell, SML, Scheme and dozens and dozens of other languages.
If you don't care about C/C++ compatibility, then it's no longer meaningful to compare D to C++. Then you have to compare it to every other language, because every other language would be a valid alternative. And then, in most cases, there's no reason to stick with the C family of languages at all. Then you could go for something modern and high level, rather than going for the incremental improvements that D offers.
D also has a few problems, compared to C++:
Because it's evolving so quickly, and because it doesn't have the same "industry standard" status as C++, there aren't a lot of tools or libraries for it. Compilers for it aren't as widely available as for C++, IDE's are rare, libraries may be written for older versions of the language.
I think D is going to remain a niche language because it tries to solve the wrong problem. It tries to be a better designed C++, which just isn't what the world needs.
If we want better designed languages, we ditch the C family entirely, and go for, say, Python, or Haskell, or Lisp, rather than "yet another incremental improvement over C".
And in the cases where we want portability, we stick with the old, familiar, stable and mature languages: C and C++.
In cases where we want compatibility with legacy C/C?+ code bases, we stick with C or C++, because no other language solves the problem.
There can be little doubt that as a language, seen in isolation, D is far better designed than C++. But that's because it ignores most of the constraints that C++ had to evolve under, and those constraints are the main reason why C++ became popular, and the reason why C++ is still popular.
So if you ask from a theoretical computer science point of view, as someone interested in programming languages, yes, D is great, and compares very well to C++.
If you ask "is D a good replacement for C++", probably not. And I doubt it'll ever become that.