> The other low level languages such as C++, Rust, Zig, ... are equally close since you can express the same things.

C is not just low level friendly, but low level out of the box. That is the level that all C must be written in, even when creating higher abstractions.

Some higher level languages are also low level friendly, not low level strict. Which is a kind dual.

I would argue that what makes C lower level, is that it comes in at, or under, the low levels of other languages, and its high bar comes in much lower than the abstractions built into other languages.

Forth is a good candidate for being even lower level.

But if someone else doesn't see things that way, that is fine. It is just one lens for comparing languages.