That niche is "code that needs to be portable to any system with a C compiler", or "... to a particular system that only has a C compiler" so i am not sure it can.

There are lots of projects using C that aren't in that niche, but i don't believe there is a good reason for any of them to be using C over C++ these days. It's either history, inertia, or Luddism.

We're not using string based macros, but hygenic macros.

We're not using goto error, but instead RAII.

We're not guessing if a function returns 0 or 1 on success and if the big struct we passed in as a pointer is valid on either of those, we're using an ADT that makes it clear.

Slices mean everyone aren't reimplementing 1000 morphs of the same buffer struct.

And the deeper separation between code and data that the fat pointers give you and how the more you go down OO principles, the less idiomatic it feels, really feels more like a giant C codebase than a C++ one to me.

You would think that, but for example I think that, for example, Oxide should definitely have picked zig, if it were more ready. Obviously it's not, and oxide wants to ship now.