That is absolutely not true.
Remember that The Hunger Games is for young adult readers. This is a series that would absolutely be an adult fiction series in the 80's. Remember, that was the time when you absolutely could not show on screen death in a children's show? Remember those days? The idea that what was suitable for children was more mature than what is suitable today is flat out false.
I know there's this myth that's perpetuated about children these days been all coddled and protected and whatnot. It's not true. Good grief, you get on screen murder in Harry Potter. Not just someone getting killed, but, flat out murder. You would never, ever get that pre-90's in a children's product in America.