Dirk, I took the liberty to download your picture and at full size it does look un-sharp. Reducing the size to 30% gives a reasonable shot, which would just meet site standards. I have not checked your camera settings nor your type of camera, and I don't know what image size your camera is shooting, but in the end a picture such as this cannot be enlarged to the extent you obviously did. It becomes blurry, un-sharp and indeed does no longer meet site standards.
There is no need to point at other pictures from other photographers or even at other shot by yourselves, this shot simply is not good enough for the site.