When one of the main arguments people use to stick to C++ is that it "runs everywhere", it actually is. After all, what use is there for a C++ where the vast majority of the library ecosystem only works with the handful of major compilers? If compatibility with a broad legacy ecosystem isn't important, there are far more attractive languages these days!

Just like Python was to blame for the horrible 2-to-3 switch, C++ is to blame for the poor handling of modules. They shouldn't have pushed through a significant backwards-incompatible change if the wide variety of vendor toolchains wasn't willing to adopt it.