The reboot series changed over the course of its run. Season 2 and 3 did not give off the same light hearted vibes that season 1 did. Especially the last adventure
About ducks, maybe there are two ducks species in this universe: anthropomorphic and a normal one. About humans, maybe they aren't evwen exist in DT universe.
They called the finale the last adventure but that doesn't mean it's the last adventure. They Defeated FOWL and Kept Adventuring. That was the whole point of the episode. And it was the Whole Reason they Defeated FOWL