The short answer is that many, many things are on the radar. That said — let me painfully try and extend the metaphor — sometimes a new squadron of fighter jets flies onto the radar and we have to stop paying attention to that slower group of bombers in order to focus on the new threat. Point is, things have to get dropped or pushed out for numerous reasons. As your example of Amazon shows (and I’m sure we could think of countless others), even noting that something is “on the radar” amounts to a promise for a lot of people.
I can say that I follow Product Wishlist and forward threads from it on to the Product Team where they get discussed. This isn’t just a place for you all to shout into the ether, as I hope the Released Features subcategory shows.