C is simply unforgiving, amateur or not.

I see a huge semantic gap between assembly language and C.

An assembly language program specifies a sequence of CPU instructions. The mapping between lines of code and generated instructions is one-to-one, or nearly so.

A C program specifies run-time behavior, without regard to what CPU instructions might be used to achieve that.

C is at a lower level than a lot of other languages, but it's not an assembly language.

C is a programming language. It makes for a very shitty high level assembler.

Here's a trivial example clang will often implement differently on different systems, producing two different results. Clang x64 will generally mul+add, while clang arm64 is aggressive about fma.

    x = 3.0f*x+1.0f;

But that's just the broad strategy. Depending on the actual compiler flags, the assembly generated might include anything up to multiple function calls under the hood (sanitizers, soft floats, function profiling, etc).

What I was thinking was something like the difference between "what" and "why". I probably could have worded that better...