Adobe actually does provide clear guidelines on what is acceptable and advice on how to achieve it. Have you read all the info posted on the "Learn and Support" pages? Adobe definitely has a higher quality standard than other sites; it's their point of differentiation to be able to offer high quality images from within Adobe Apps. Adobe Moderators do NOT reject all images; that would be a going-out-of-business proposition. My rejection rate initially was 20-25%, until I learned to inspect all of my images much more carefully before submission. Once I learned to do that, I seldom have a rejection for a technical reason - usually only an IP rejection which is kind of a guessing game for contributors.
You still haven't posted any of your images for critique; should you decide to do so the helpful community members will be glad to comment.