It could have still been rectangular. All they really needed to add was a key to the housing of the connector. (Logic being that an odd shaped metal connector would be just a hair more expensive to manufacture than just adding a key position to an injection mold.)

Trapezoid or key, it would have still been a pain when trying to insert the connector blind. Having fingered thousands of different connectors (lulz) over the years, it is still difficult to feel the orientation of a recessed female plug, regardless of its shape.