If someone is using a vector for a small array of fixed size in C++, in a place where performance matters, then their knowledge level is so low that you are going to have issues with them no matter what, I'm afraid. Knowing that vector uses the heap is beginner level knowledge.

On the other hand, in C you are stuck with a built in array now. If you pass this to a function that doesn't get inlined, it will decay into a pointer, then inside that function the compiler has actually "lost" knowledge of the size of the array. Now you have to pay for a loop.

In C++ you can pass a std::array by const reference, the compiler knows exactly how big that array is at all times, and for small arrays the loop checks can be eliminated entirely.

Many of the arguments against C++ boil down to: if you're working with a lot of people who have a knowledge level below what I would expect someone with 1 year of good experience to have, then they can make more mistakes. Is the level of developers generally really that low?