The C23 edition of Modern C

Most important aspect of C is its portability. From small microcontrollers to almost any computing platform. I doubt that any new version of C will see that much adoption.

If I want to live on cutting edge I would rather use C++2x or Rust rather than C.

Am I missing something? What benefit this supposedly modern C offers?

these features will eventually trickle down into the mainstream, kind of like C11 is doing at the moment

also, unless you're targeting embedded or a very wide set of architectures, there's no reason why you couldn't start using C23 today

Or in other words, for embedded and existing code: most use c99, some use c11 and nobody uses c23 until at least 10 years from now.

This depends on the platform. Many embedded systems are based on arm these days and have modern toolchains available.

I cannot remember the last time I saw C99 used. C codebases generally use C11 or C17, and C++ code bases use C++20

Unless you can vouch for the C++ compiler, the best C++ portable code can offer today is C++17.

Also 8 and 16 bit embedded toolchains are certainly not on C11 / C17, they can hardly afford full C89.