Yes, most language features past the C89 subset are not supported, besides the C standard library, because C++ has much better alternatives, like why _Generic when templates are a much saner approach, than type dispatching with the pre-processor.
However that is besides the point, 99% of C89 code minus a few differences, is valid C++ code, and if the situation so requires, C++ code can be exactly the same way.
And lets not forget most FOSS projects have never moved beyond C89/C99 anyway, so stuff like _Generic is of relative importance.
As for WG 14, they incorporated numerous C++isms into C. While you claim that they did not go far enough, I am sure you will find many who would say that they went too far.
I claim they aren't focused on what matters, we don't need C++isms into C, we already have C++, and C should have been done as language back in C89.
Anyone that wanted more has always been able to use C++ instead, or Objective-C on Apple/NeXT land.
What we need is for WG14 to finally take security regarding strings, arrays seriouslys, not yet another reboot of functions using (ptr, length) pairs.
I have tested this WRT _Generic as it was a concern. It turns out that GCC will accept it on older versions, which permits compatibility. You might feel that this is wrong, but that is how things are right now.
