You can't always know, and that's the thing, if you want to explore and find new places, you don't want to rely on social media! Others we just keep going to same boring places.
Australia isn't an inherently dangerous country. We SHOULD be able to camp alone, that's the thing.
But we are certainly more prepared for next time - we could have camped a mile up the river where you could only fit one car in. Not the beach, but at least a beautiful spot.