Airdrop Over Wired Connection?
Open Image Capture or the Photos app on the Mac and connect the phone over USB. That's the easiest way to pick one photo to import.

Other methods involve setting up sync or some apps to do the syncing if AirDrop is not reliable enough for your needs. (you're not alone there on depending on it - wireless interference that can be reasonable encountered these days can render AirDrop less than reliable in my experience)