If it's so hard to find I can't imagine they'd care what you have to say. Besides, it's not my packages I see thrown 10 feet across someone's yard. It's my neighbors that I don't know and wouldn't recognize if I saw them. For all I know it's not even Amazon handling the deliveries since they come in an unmarked white van.
Then it's not your concern if you don't feel you should tell your neighbors. I was replying to someone who said they saw something happen with their own package and I can assure you from extensive experience that Amazon goes out of their way to try to make it right with the customer (even if they don't address the root problem, they still do something to make it right to a complaining customer).
https://www.amazon.com/gp/help/contact-us/general-questions....