What was a class? A class was a special designation by the system that allowed a sapient entity to walk upon a path they chose. There was no being in the Boundless universe that did not have a class.
From a mere farmer to a king, everyone had a class. There were more classes than there were strands of wool on a sheep.
Some classes were archetypal, or common. Swordsman, mage, rogue, shield bearers, clerics, druids, etc. Every other class was a variation of one or more of these, and could trace their roots to them.
Classes were diverse because sapient beings were also diverse. A sign of sentience and cognition was individualism. Instead of obeying nature strictly, or thinking with the community at heart, a sapient being prioritized itself first.