D is in a tough situation right now

I think its good all around and balanced languages, but, there is always a better language for any use case, where D is an alternative

Ocaml, if you want performance close to C/C++ plus and high level abstractions

Rust, if you want manual memory managment

C# and Java, if you want large ecosystems and advanced features

Also C++ is now moving and improving fast Even Ada is sort of making a come back

I'm curious about the Ada comeback - do you have any examples? I know it is still used in space & defense, but I thought those were legacy code bases.

Well, I would recommend you search for Spark, and check the website of AdaCore

But, I would suggest that investing in Rust might be more valuable for one's career I am learning a bit of ADA, only for educational purposes and to scratch an itch, it is very different from anything I used, and I like that

I'd argue D is better than all of those in some ways.

D development is lively and active. I enjoy the language, and I plan to keep using it as long as I keep enjoying it.

That looks really interesting. Is this all done at compile time or runtime? After further reading the answer seems to be compile.

Definitely compile time. D has a somewhat similar feature called contracts (https://dlang.org/spec/contracts.html) which happen at runtime, but don't influence function/template resolution.