+1 to what Geoff has written.
Everything under a bridge, underpass, flyover, etc, will be shaded, which means the areas past it will tend to be much brighter. That is what has happened here; the people and other things are in a darker area of the scene and are properly exposed. The areas beyond it are very bright to the point where the sky is close to clipping.
The human visual system is keyed to see areas of brightness or of high contrast, so the tendency is for our eyes to notice the very bright sky in the background, so that weakens the overall impact of the image.
You should also watch what is happening around the edge of the image. The cut of legs that Geoff has mentioned, the bit of green in the bottom left hand corner and the gap between the pillar and the edge of the image all weaken the composition a bit.
Concentrating on the people and eliminating distractions, such as the historical building in the background will also strengthen the image.