Not everything has to be trying to be stopping an invasion of slaadi. Those rats in the tavern cellar aren't going to get cleared out on their own.
If the main payoff from playing the game is imagining my character defeating foes, I think rats may be a rather non-compelling foe.
If I'm being invited to imagine my character in such an ignominious context, I need something else at stake in the fiction to make it compelling.
I would argue the main playoff is "overcoming obstacles."
Sometimes those obstacles are compelling foes. Switching it up, of course, keeps things interesting!
Asking a bunch of adventurers to, say, clear out rats or help get someone elected or plan a feast allows the players an opportunity to use their abilities in new, fun ways!