The Borg don't seek perfection by extinction of the physical body; even the queen in her disembodied state retains her torso. They seek it by assimilating other cultures; and their creativity is also arrived at through this method. It is an excellent approach, since mongrels are stronger than inbred animals. They have the diversity to avoid inbreeding pitfalls.
If the Borg suddenly decided just to go with what they have and replicate current technology, they would eventually encounter problems of inbreeding and outdating. In addition, since they do use the assimilation approach, it is required that they maintain bodies similar to the ones they assimilate, in order to both do the work of assimilation and continue on in those bodies.