C is a terrible cross platform assembly b/c it doesn't allow you the level of control which one would expect in this day and age. Maybe it was written in the days when CPUs were brain-dead simple, but basic things that are available on most architectures aren't part of the language. It has no notion of a CPU cache, it has no notion of branching (you can't tag a likely branch and an unlikely one), it even goes as far as to ignore user keywords for inlining and provides no keyword for blocking inlining. RVO is implicit magic that you just pray happens. Const != immutability.
When you write C you have no notion of what the compiler is going to output whatsoever
A lot of these things are available through compiler extensions (so great, now it's not cross-platform), but even still the language is broken. "Expert C Programming" has a really long chapter that goes over all the more confusing subtly problems C has beyond just arrays being pointers-but-not-really.
I have to use C pretty regularly and all I can think is "God.. why hasn't anyone made this better yet"