In this case, the fg being dark is a good thing! Silhouettes are great! My only problem with this image is that you have cropped off the fg too much. I would like to see a bit more so at least the peoples feet are not cut off.
The two trees cutting the photo into three parts could have been a bad thing, but somehow i think it is ok here. It works for me. The herons flying through the sky, which was the whole point of your shot in the first place, adds an interesting element in their flying over the people on the walk.
I like it, but want to see a little more foreground.
If you do not have more fg in the original, MB1's suggestion could work to help get something more of this.