> The big issue is lack of technical resources to improve GC's performance on D's runtime.
The underlying issue is that to make the GC more performant requires the addition of "write gates", where writing through a pointer notifies the GC that the memory object has changed. This is a reasonable choice when a language is heavily GC dependent (like Java).
However, D is not at all heavily GC dependent. But it is very dependent on memory references. Hence the GC speedup from adding write gates would be more than lost from the cost of executing those write gates.
Some improvements have been made lately, but not at the level of manpower and CS background from other GC enabled languages.
I am quite confident that if D had something like Microsoft behind it, its GC would long be as good as Sing# or System C# (M#) were.