Maybe the drones operate along aerial highways, and use a Wile E. Coyote-esque claw to release their payload on a parachute?

Over every home enough that the only worry of the drone is dodging yard stuff (trees, and buildings, mostly?), at least.

If we could all have landing pads like we have mail boxes, something with a fence, it would be much better.

So major cities are just one big pre-defined 'corridor'? What's the point, may as well just un-restrict it at that point?

You are generally want to have corridors so that you know where the drones are going to be, so you wouldn't just unrestrict everything, you'd have specific paths that the drones need to take to and from their destinations, like roads on the ground.

You don't leave it free space because then you have all sorts of drones whizzing around in all sorts of random and uncontrolled directions and that creates a lot of clutter that will cause crashing.