I have been in the D community for a very long time. I have seen D successfully deployed in companies, and the pain points associated with it. I have seen D fails to catch on in companies and why that is has well.
Let me tell you, none of this has anything to do with feature D has or does not have. At large, D has more features than most languages.
D chasing the next feature like a crack addict chase his next dose. With the same level of success.
The main problem people face with D in the real world are almost exclusively of the implementation kind. The list is endless (and yes, there are many bugs reports about these things). I recently made a post about how the OOP implementation is extremely sub-par vs what people in OOP languages would expect. no change of the language required to fix. See here: https://forum.dlang.org/post/hteuczyclxajakrisxjd@forum.dlang.org
But if you are not convinced, here are a few more example of thing being implemented wrong or existing feature not working right:
- D runtime is unable to see thread started manually (for instance with pthread-create) leading to all kind of bizarre behavior.
- Template symbols are generated as weak, which prevents inlining (!).
- Pretty much no cross module inlining, making helper function absurdly costly.
- scope(success) generates exception handling code.
- D goes virtual by default for class methods, but LTO is unable to finalize (contrary to every other languages going virtual by default).
- The GC implementation is nowhere close to where it needs to be.
- in contracts are dynamically bound (and in the callee) instead of statically bounds and in the caller.
These are just simple thing that I have on top of my mind, but there are a ton more. I have seen some of the above cause projects to fail. None of them require any significant language change.
There is nothing features like string interpolations or named argument can bring to the table that could pay for the implementations problem of existing feature. The cost benefit analysis is just a big L for D: the fail to address the main pain points, while causing massive breakage in the tooling ecosystem (syntax highlighting support in 3rd party IDE, code formatter, etc...), and it cost real time and resource to upgrade these, or come at the cost of other quality of life stuff nullifying their benefit (for instance, the quality of syntax highlighting for D has degraded significantly in vim and sublime text over the past few years).
In addition, some recent D features, such as @nogc, has been a productivity disaster int he wild. While the impact might not be felt on smaller codebases, the infectious nature of the feature makes large codebase significantly harder the refactor than they used to be.
Each time we take steps in that direction, D becomes a harder sell.