Don’t blindly prefer emplace_back to push_back

Random emplace_back hate: I really dislike how you can't use it for objects that you'd normally use aggregate initialization for.

See https://godbolt.org/z/6qW7q3

    struct SimpleData
    {
        int a;
        double b;
    };

    SimpleData someData = {1, 2.0}; // ok

    std::vector<SimpleData> data;

    // Why can I not do this?
    data.emplace_back(1, 2.0);