From GameWatcher: “Assassin’s Creed Odyssey is, much like Origins, a fully-fledged action RPG instead of being an action-adventure title like the earliest iterations of the franchise. This means that with it come all the usual features of RPGs, one of which is levelling, too.”
Source: N4G PC Assassin's Creed Odyssey Level Cap – What is There to do When You Reach Max Level?