Why are some types from std not in the core of the language?

[zjh]

On Sunday, 12 June 2022 at 14:29:41 UTC, zjh wrote:

> `DMD` needs radical refactoring.
> `The source code` is too bad. `Divide` large files into `small 
> files` and do `class encapsulation`!

D should stop `'D2'`, develop `'D3'` and radically refactor 
`'DMD'` for `'D3'`.

What should we do if even `experts` can not 'correctly and 
completely' realize new features?