Iwo Jima Memorialby
allizoeComment by KaDi: Greetings from the Critique Club! Per your request I am offering and "in-depth comment" on your entry...I hope you find it helpful. Also, welcome to DPC and congratulations on entering your first challenge. (The first challenge is often the most difficult.)
The subject you chose to represent "triumph" fits the challenge fairly well. However, I agree with some of the comments you received that it is mostly a representation of someone else's idea--in this case, the sculptor and the photographer on whose work the sculpture was based. It's good to try to bring your own interpretation to the subject, even if it has as its subject a sculpture (or other piece of artwork). Viewers want to see your own interpretation of it, something new. A few other mentioned including fireworks or a sunset...including unique elements like those can make your photo stand out.
Technically the photo has some common problems that hurt its reception by the voters. The shadows are so black that much of the detail has been lost and the light on the flag so harsh that it has also lost detail and contrast. It looks like you took the image in full noon sun when getting a good exposure is difficult. Cloudy days and morning or evening light are generally more successful times to take images like this one.
The composition lacks some strength. Including tree branches as you have done here can add framing and scale to an image...but because they only peek in from one side in this image it does not work so well. Here it looks like they mistakenly intruded into the frame. Having some to the other side would provide balance and indicate that their inclusion was intentional. Finding a different angle to take the image could help. Getting in closer to the subject and only taking a portion of the sculpture might make a stronger composition, too, showing us what you found really compelling about the subject and simplifying the presentation so the viewer knows where to place attention.
Overall, you met the challenge in a sort of scavenger-hunt way. I think you'll find that to really succeed in a DPC challenge you need to bring a bit more of yourself to the image...go a little beyond the "hey look what I found" and more toward showing us how you feel about the thing you found.
Good luck! Keep shooting!