You can enjoy any campaign - even one set in an Age of Discovery like the Last Continent - without any fancy classes. The “core four” presented in OSE Classic Fantasy - Cleric, Fighter, Thief, Magic-User - cover the basic archetypes and allow for endless variations. In fact, many argue that every character boils down to either Fighter or Magic-User.
However, a referee can use unique character classes to convey certain truths about a setting. A Cleric class insinuates that either monster hunters or crusaders - religious zealots of some sort - are commonplace. If the Cleric instead gets branded as a Missionary, that probably means they rely less on violence and more on social skills. It also strongly suggests that they seek to convert people to their cause.
Most of the classes used in the Last Continent take familiar abilities and remix them to fit better in the flavor and tone of the setting. For instance, the class showcased here - the Minuteman - takes the abilities of OSE Classic Fantasy’s Halfling class and frames them as those of a hardy frontiersman. It really can be as simple as that. My players have been using this class for nine months and have yet to realize that it's a "re-skinned" Halfling.
Minutemen wearing +1 tricorns of scowling |
The Minuteman class draws inspiration from stories of early American colonists who styled themselves as a reluctant militia defending their homes and livelihoods from British oppression. American poets later romanticized these legends in works such as Emerson’s “Concord Hymn” and Longfellow’s “Paul Revere’s Ride.”