Why is the Visual Studio Community 2017 C++ standard C++98?

The value of __cplusplus is temporarily intentionally non-conformant by default for current versions of Visual Studio in order to avoid breaking existing code. It does not mean your compiler does not support any C++11 (or newer) features.

Quoting from MSVC now correctly reports __cplusplus:

/Zc:__cplusplus

You need to compile with the /Zc:__cplusplus switch to see the updated value of the __cplusplus macro. We tried updating the macro by default and discovered that a lot of code doesn’t compile correctly when we change the value of __cplusplus. We’ll continue to require use of the /Zc:__cplusplus switch for all minor versions of MSVC in the 19.xx family.