The basis for taxonomy is a recent development
The basis for our current taxonomy system was developed by a Swedish botanist named Carl Linnaeus about 250 years ago. It stemmed from his studies in botany and how poor the classification for plants was during his time.
Viruses are classified using the recognised taxonomic system
Taxonomy is the classification of all living things. Because viruses are not considered to be living, they currently do not have a place within this system. This may change in the near future.
Everything is perfectly categorized in the taxonomy system
Because taxonomy is involved in grouping organisms, the idea is to create groups in which organisms either are put in a group or not based on the presence or absence of a specific trait. There are instances where exceptions are made and an organism is placed within a group for reasons other than the fact that they have a similar trait