The only reason the Cardassians were any good at all was because there was two great actors playing to pretty good characters. As a whole, they were extremely uninspired.
It would be really easy to make an argument that, conceptually, the Borg work better as an adversary to Kirk than they do to Picard.Why?
Kirk versus computers is a running theme in TOS. The Borg would be the ultimate culmination of that theme.