Re: New submission limits for Adobe Stock Contributors

You are playing roulette by resubmitting your rejected assets multiple times. As stated previously it's okay to resubmit after editing to address the flaws, but if that image gets rejected again, move on. You are putting your account at risk of suspension for spamming. 

Why is it that many photos get denied on the first attempt, then accepted on the third or fourth attempt?

By @ZALEZPHOTO

Because you are spamming the system. There is always a chance that you get a new moderator checking your assets the fourth attempt, and that the moderator does not see the issues with the image. At some point, I fear that this could lead to your account being blocked.

and also, in the library I see a lot of beautiful shallow depth of field photos, yet when I submit, many are automatically rejected.

By @ZALEZPHOTO

No assets get "automatically" rejected. A shallow DOF needs to be logical. It's not that because you take a picture at f/1.4 with a top lens that the picture is a good picture.