Distance between application programming and standard library programming

This is a rough, potentially half-baked thought:

This might an interesting metric to compare programming languages: distance between application programming and standard library programming.

In general, standard library programming is more difficult than average application programming for any programming language. Or at the very least “different” in some way — language features used, programming style required, etc. That difference might vary depending on the language.

Mainly, I’m thinking about C++, where standard library programming requires expertise in C++ template meta-programming (TMP) (i.e. to implement std::variant), which is effectively an entirely different programming language, existing in the C++ type system. While many application developers may also be competent in TMP, there are many that aren’t (including myself). It’s possible to be a very productive C++ programmer, and STL user, without being an expert at implementing generic libraries using TMP.

Given this, my impression that C++ has a relatively high distance between application programming and stdlib programming.

Python of course also has some distance here. I’m not qualified to speak on it, but I can imagine it also involved more obscure language feature that do not occur often in normal app development. I would guess that this distance is less than C++.

Lastly, C is an interesting language to consider because it offers such a spartan feature set that there aren’t particularly that many more language features available to be used. (I’m probably wrong here and there are obscure things I’m not aware of, including symbol versioning for compatibility). But in general, my assumption would be that C has a some limited distance, given it’s restrained feature set.

Ultimately, this metric is probably impossible to quantify and may have limited value, but is something I find intriguing anyway if it were to exist.

Any thoughts?