Here's a checklist:
Dog Days doesn't have an Inactivity timer, so you can actually get rewards by standing still
You don't actually have to kill anything to complete Dog Days, ties count as wins.
In solo, you can actually pause the game for 5 minutes and the timer will still keep going and give you the rewards.
And now here's a list of suggestions in the same thread.
Scale the rewards with kills or make kills decrease the timer.
Decrease the costs of reward exchanges. Floofs and Captura aren't worth hours of standing still.
Punish people for not helping by gimping their rewards.