C23 features won't help many C users because it's a community that takes an uncommonly long time to move to new versions. Linux only recently moved from C89 to C11.
As long as Linux doesn't prevent user space code to be written in more recent C standards (which it obviously does) it's fine.
Apart from that, there's also the Visual Studio compiler team to blame because they didn't manage to catch up with C99 until around 2015 (and even then only an incomplete implementation), and only in 2019 decided to 'officially' support the latest C standards again.
In general it makes a lot more sense today to start new C projects in more recent standard versions then it was 5..10 years ago.