With that background of rejection it is rather frightening to realize that I'm expected to come up with something good. It's much easier to write something you expect no one but a slush pile editor to glance at anyway. On the other hand, though the process might be a little more difficult, there is much, much more incentive to persevere. Trying to provide interesting mysteries to puzzle over is always a challenge, and we hope that folks enjoy reading them as much as we enjoy writing them. Don't take rejection to heart.
Editors like to give reasons for rejections in terms of professional evaluation.
Mostly it's a matter of personal opinion. Often the difference between being published and unpublished depends upon the manuscript falling into the hands of the right individual. And finding a talented co-author. One of the first non-fiction pieces I sold concerned the British custom of swan upping. Each summer, along a particular stretch of the River Thames, all the wild swans are captured temporarily to have their beaks nicked with a very slight mark.