I hear this a lot. It’s also untrue. If you are open to anecdata, it’s trivial to prove this is untrue.
What people constantly miss and fail to consider is what they are working hard at. Hard work is a requirement for success and class mobility, but it is not sufficient. You must also work hard at the right things.
The truest thing I have learned about life is that you need to do three things to be successful:
1. Identify places where you can add value /for people who can compensate you/.
2. Learn how to articulate the value you add.
3. Ensure you get compensation for that value added.
If you do these three things, your hard work will pay off, maybe in a big way.