> "What real advantage does the switch to C++ from C have for you?". You can find vast amounts of information on the web to answer that question :)
As well as vast numbers of religious flamewars. I'm personally of the camp that (C || Fortran || "C with classes") + (Java || C# || Python || ${HIGHER_LEVEL_LANGUAGE}) is better for nearly any complex, performance-sensitive task.
People also have this false preconception that you have to write everything in Fortran77. You can keep a F77 codebase alive, while writing Fortran 90 (0) code which is surprisingly modern, has amazing mathematical computational performance (especially with Intel's MKL and compiler), and the language has amazing OpenMP integration.
I'm with you on combining the best tool for the job and sometimes having a Java/C/Python wrapper is useful, but you can retain your Fortran tried-and-true-and-tested code-base while adding feature enhancements compiling against the Fortran2003 standard and often eliminate the need for wrappers. I guess the practical problem is finding F2003 engineers is way more challenging than a Java or C# dev.
0: F90 was the "big" upgrade that came out which made Fortran "modern", but there have been continuous upgrades like F95, and Fortran 2003 (I guess this would be analogous to C++17) which make it perfectly fine to write.
As well as vast numbers of religious flamewars. I'm personally of the camp that (C || Fortran || "C with classes") + (Java || C# || Python || ${HIGHER_LEVEL_LANGUAGE}) is better for nearly any complex, performance-sensitive task.