> There is a lack of standardized RAII wrappers for handle types like there is for pointers.

.. what's wrong with

    #include <memory>

    template<typename T, auto Free>
    using safe_handle_t = std::unique_ptr<T, decltype([] (auto p) { Free(p); })>;

    using file_handle = safe_handle_t<FILE, fclose>;

    void file_example() {
        file_handle f{fopen("foo", "r")};
    }