Why is visual studio code telling me that cout is not a member of std namespace?

Its a bug.

There is a workaround for this bug, go to File -> Preferences -> Settings in VS Code and change

"C_Cpp.intelliSenseEngine": "Default" to "C_Cpp.intelliSenseEngine": "Tag Parser"

I am using VSCode version 1.22.2 with MinGW compiler and below config works for me:

{
"configurations": [
    {
        "name": "MinGW",
        "intelliSenseMode": "clang-x64",
        "compilerPath": "C:/MinGW/bin/g++.exe",
        "includePath": [
            "${workspaceRoot}",
        ],
        "defines": [
            "_DEBUG"
        ],
        "browse": {
            "path": [
                "C:/MinGW/lib/gcc/mingw32/6.3.0/include",
                "C:/MinGW/lib/gcc/mingw32/6.3.0/include-fixed",
                "C:/MinGW/include/*"
                "${workspaceRoot}",
            ],
            "limitSymbolsToIncludedHeaders": true,
            "databaseFilename": ""
        }
    }
],
"version": 3
}

Refer these link too: https://github.com/Microsoft/vscode-cpptools/blob/master/Documentation/LanguageServer/MinGW.md

https://code.visualstudio.com/docs/languages/cpp