It was a bad idea for them to give all the Borg instant assimilation powers. Assimilation should've been something they needed proper equipment to do, on their ships.
On the other hand, it was a welcome retcon to add nanotechnology to the Borg's bag of tricks. The original conception of Borg technology as this clunky, macroscopic, mechanical stuff surgically grafted onto bodies was already outdated when the Borg were first introduced.