I worked on a C++ codebase that was essentially C with a few obvious domain classes and the addition of std::string and std::vector for convenience. I suspect that this is quite a common space, and it's immune to the march of the whizzy new features that are being added. Probably the only remotely modern bit of C++ that we could have benefited from is a salting of std::moves to remove some redundant copying, but this wasn't really worth the candle tbh.