What you consider to be the background may not be what Alamy or a buyer considers it to be. If any part of what could be considered the subject is not good and sharp at 100%, then don't upload it no matter how much you like the photo. Unless you know more about what sells than I do, taking a chance on QC failure just isn't worth being locked out on all the images. Note that blurred backgrounds are perfectly acceptable, just not soft subjects. QC gets to decide what the subject is, not us.
Also, and many beginners make this mistake, don't assume that deleting the failed image gets the job done. QC only checks a sample of the submission, so others in the set may also be soft but not noted. When you delete only the one(s) that QC noted, and resubmit the other ones, there is a good chance that QC will find another soft one and fail you again. Always recheck the entire set that was rejected at 100%, and delete anything that is the least bit doubtful.
Most of us have had failures before we learned what would reliably pass, so don't take the first few failures personally. Just accept that fact that when you are making a normal submission to Alamy, it has to meet their technical QC standards. Period. Alamy QC doesn't give you any credit for composition or possible salability.
Also, go over the sky or any other uniform area several time to look for sensor dust ( also called dust bunnies ). They are easy to miss, and QC has real talent when it comes to finding them and failing the image.