The Borg's biggest mistake was not assimilating and cloning the Ferengi early on
Think of the Super Borg they could have built out of Ferangi. Yes they are often shorter than the average humanoid. But many of a Borg's most useful attachments are on its arms and its head.
Can you imagine how many sensors, scanners, weapons and other attachments you can fit on a skull the size of a ferengi? With that lobe spread?
Compared to the skull of a human it would be like the difference between outfitting a Saber class and a Galaxy class starship.
Are Borg stupid?