It was competing with C and Java when it came out. People who like C will not use a language with garbage collection, even one that allows you to not use it. Against Java, it was a losing battle due to Java being backed by a giant (Sun , then Oracle) and basically taking the world by storm. Then there were also license problems in early versions of D, and two incompatible and competing standard libraries dividing the community. By the time all these problems were fixed, like a decade ago, it was already too late to make a comeback. Today D is a nice language with 3 different compilers with different strengths, one very fast, one produces faster results, and one also does that by works in the GCC ecosystem. That’s something few languages have. D even has a betterC mode now which makes it very good as a C replacement, with speed and size equivalent or better than a C equivalent binary… and D has the arguably best meta programming capabilities of any language that is not a Lisp, including Zig. But no one seems to care anymore as all the hotness is now with Rust and Zig in the systems languages space.

"We all know of the language and chosen not to use it."

Is a strange claim, and hard to cite. But I think many HNers have tried out D and decided that it's not good enough for them for anything. It is certainly advertised hard here.

Maybe you should Ask HN.