I notice many threads of people talking about how they don't like the tap-to-focus, or they simply forget to focus.
I have mine set on auto focus, and I had no issues at all.  I was flying near trees, verifying they're in focus, then quickly climbing in altitutude to focus on buildings a quarter mile away, and they would be in focus with no issues at all.

Why do you all have yours in manual focus mode?

The lens on the Mavic does not focus by itself as it passes by various objects.  You need to tap on the screen to focus on things at various distances.  Just because it says AF on the controller doesn't mean that the lens is doing what you think it's doing.  I suspect in your case, you had the lens focused on a far distance and most things seemed to be in focus to your eyes.

Try setting the Mavic on a table and see if it focuses on near and far objects as you point the lens at them.  You'll see that it doesn't change its focal length without tapping on the screen.

When I had it sitting on the sidewalk before take off, I noticed the grass and texture of the sidewalk were in focus.  As soon as I took off, the trees further away were in focus.  Flew up even higher and buildings very far away (but centered in my shot) were in focus.
I'll try and take a video showing near to far focusing.

Username Taken Posted at 2016-11-21 10:47
When I had it sitting on the sidewalk before take off, I noticed the grass and texture of the sidewa ...

Make sure you are viewing these scenes on a full size PC monitor and not just on your phone.

Post 2 is a good example, set it inside or outside and you can see how the focus works. You can manually set it to infinity and that should be a good point to have everything in focus except close up.