ok, I can buy your analogy on blurness vs focal length.
When I first saw your pic and message, I interpreted that you can't get a slow enough shutter speed to achieve the blurness you wanted with a wide angle lens. Obviously, technically speaking, this is incorrect.
You mentioned you wanted more blurred people in the background, presumably a sharper people in the foreground. But, the thing is, I can't see how you can differentiate background and foreground people in the picture in questioned, especially at that perspective and distance.
If you rather wanted to capture the jostling atmosphere of Chinese New Year at that distance and at that lens perspective, a long exposure of minimum 4 to 8 seconds would be ideal, depending on how jammed the human traffic is.
Then you "confessed" your shutter speed was 1/15 sec because you left your 3-legged friend at home, I think this is a mistake.
But, I quite like your perspective of this picture.