Something that gets neglected in these discussions is skill relative to the wind as well.
When the wind is right in the easy middle range, everyone can make the boat go. There is enough power to keep things moving and enough time to make adjustments if needed. The less skilled sailors start dropping out the back of the fleet as soon as the wind becomes very light or very heavy. Reading the wind and maintaining momentum in very light stuff, or maintaining speed and control in the heavy conditions both take a lot more skill and time to master.

If you use the same techniques etc to sail the boat in heavy air as you would in light, you are going to be very slow. Same for weight; if you try to hit the same angle of attack etc, you are done and flushed out the back. The extraordinarily bad finish is not a weight issue it is still the driver. Sail the boat for the conditions, crew and wind, and you will be very competitive over a very large range of both.