Actually, C, FORTRAN and C++ are friendly to memory bandwidth, written correctly.

C++ is better than FORTRAN, because while it's being still developed and quite fast doing other things that core FORTRAN is good at is hard. At the end of the day, it computes and works well with MPI. That's mostly all.

C++ is better than C, because it can accommodate C code inside and has much more convenience functions and libraries around and modern C++ can be written more concisely than C, with minimal or no added overhead.

Also, all three languages are studied so well that advanced programmers can look a piece of code and say that "I can fix that into the cache, that'll work, that's fine".

"More modern" programming languages really solve no urgent problems in HPC space and current code works quite well there.

Reported from another HPC datacenter somewhere in the universe.