The code model cannot be convinced to treat the project as C++11, C++14, C++17, ... It's stuck interpreting it as C++98.

This reproduces using both cmake and qmake projects, either MinGW or MSVC compilers. All cmake options related to language standard are ignored. Qmake's CONFIG+=c++14 is ignored as well. The following were tried in cmake:

set(CMAKE_CXX_STANDARD 14)
add_compile_options("-std=c++14")
target_compile_features(${PROJECT} PRIVATE cxx_std_14)
target_compile_options(${PROJECT} PRIVATE /std:c++14)

This makes the annotations and the code model unusable with modern code

It is not possible to turn off all annotations. The underlines and the circle/triangle symbols in the bar on the left of the editor window cannot be suppressed - there's no option for that.

Combined with all the incorrect annotations, this makes Qt Creator unusable on Windows with any modern code.