Secondly, apparently you are talking about PIC class systems as embedded, given that even a lonely ESP32 has C++ SDK support.
Thirdly, AUTOSAR now advises C++14 as certification language.
Do you read Embedded Magazine? Most C proud devs are using C89 alongside proprietary language extensions for their target boards + Assembly, and very resistant to any kind of improvements, not even using unit tests or static analysis tools.
Old dogs indeed, I bet that until 2030 the new C++ generations will take over the remaining holdouts.