Anyway, I do not see how this affects the design of C in a way that makes no sense anymore today (except that one could require CHAR_BIT to be eight, but there are still DSPs where this is not the case). I think people repeat the "the C design reflects the out-dated PDP-11 hardware" meme because it sounds smart while in reality it is just nonsense.
So when is WG14 standardising modern hardware into the C standard?
Basic stuff like SIMD, SIMT, without requiring users to go beyond language extensions, something that any programming language can offer in similar capacity?
Why does the language standard need to prescribe everything. It is a standardization of between existing compilers, they are allowed and intended to invent things. If anything the experience from C++ has shown, that writing too much behaviour into the standard accidentally has consequences on the possible performance. The C standard is descriptive, not prescriptive.
> something that any programming language can offer in similar capacity?
By your measure a lot of other languages don't offer anything to begin with, because they do not have a standard at all, only a reference implementation.