You're absolutely right, of course - a webapp in C++ is not something that I'd want to even volunteer to help maintain. I'd just say that it's not the language

You're absolutely right, of course - a webapp in C++ is not something that I'd want to even volunteer to help maintain. I'd just say that it's not the language that rots, but the libraries, and preexisting code. There are still some areas where C++ is a good choice, but for things like a webapp, there would have to be a really compelling reason to choose it.