I wrote some stuff in D. The templates and compile time evaluations were really nice, it could do a decent chunk of what we do with Rust these days. It had reflection and other useful things. The vibe.d framework was also fairly good and impressive at the time. Actually D's async stuff is a lot nicer than it is in Rust today, but Go kinda beats it now. But being sick of scripting languages and no types, it was attractive as a reasonably high level and performant language. Java was still super crap, and dotnet was still super proprietary at the time.

But I didn't stick long because although fairly nice, it didn't take off. There's no libraries no community no jobs.

I feel like Rust is kind of a natural replacement and it's plain better. D is garbage collected but still low level and has a C FFI, which is basically free footguns for everyone. You get to do even more compile time madness and templating and macros, and it's memory safe. And the APIs are just nicer too, the D standard library is servicable but not as nice as Rust's.

They were too late to the game to try to make a semi proprietary language.