I used to think of D as the same category as C# and Java, but I realized that it has two important differences. (I am much more experienced with Java/JVM than C#/.Net, so this may not all apply.)
1. Very load overhead calling of native libraries. Wrapping native libraries from Java using JNI requires quite a bit of complex code, configuring the build system, and the overhead of the calls. So, most projects only use libraries written in a JVM-language -- the integration is not nearly as widespread as seen in the Python world. The Foreign Function and Memory (FFM) API is supposed to make this a lot easier and faster. We'll see if projects start to integrate native libraries more frequently. My understanding is that foreign function calls in Go are also expensive.
2. Doesn't require a VM. Java and C# require a VM. D (like Go) generate native binaries.
As such, D is a really great choice when you need to write glue code around native libraries. D makes it easy, the calls are low overhead, and there isn't much need for data marshaling and un-marshaling because the data type representations are consistent. D has lower cognitive overhead, more guardrails (which are useful when quickly prototyping code), and a faster / more convenient compile-debug loop, especially wrt to C++ templates versus D generics.
1. Very load overhead calling of native libraries. Wrapping native libraries from Java using JNI requires quite a bit of complex code, configuring the build system, and the overhead of the calls. So, most projects only use libraries written in a JVM-language -- the integration is not nearly as widespread as seen in the Python world. The Foreign Function and Memory (FFM) API is supposed to make this a lot easier and faster. We'll see if projects start to integrate native libraries more frequently. My understanding is that foreign function calls in Go are also expensive.
2. Doesn't require a VM. Java and C# require a VM. D (like Go) generate native binaries.
As such, D is a really great choice when you need to write glue code around native libraries. D makes it easy, the calls are low overhead, and there isn't much need for data marshaling and un-marshaling because the data type representations are consistent. D has lower cognitive overhead, more guardrails (which are useful when quickly prototyping code), and a faster / more convenient compile-debug loop, especially wrt to C++ templates versus D generics.