Earlier quoted context omitted.
C++ is just slow to compile. With the standard library it is much worse. The problem is that with C++ you're not getting as much encapsulation as you would in C unless you do extra work that also has a performance hit (pimpl). This means that C++ code often has to recompile a whole lot more than C code does when doing incremental compilation in my experience.
This is just not true. There's nothing that makes C++ inherently slow to compile. PImpl doesn't need to have a performance hit as you can implement it with a local fixed-sized buffer that's not heap-allocated. You can also design your C++ codebase exactly as you would in C, so there's literally no reason why you'll need to recompile more in one language compared to the other.
A quick google "c++ grammar" will give you clues that C++ is not you average language. Templates are also turing complete, and probably not trivial to parse.
Of course I am not talking about C++98, but C++14, 17, etc, which add significant stuff.