The issue isn't just related to the duty finder anymore it's that servers can crash if there are too many people in densely populated areas - such as the starter areas, which is why they had really limited capacity at the start and have gradually increased them as the population has spread out across all areas. Even if you are on the server doing nothing you are still consuming resources that is preventing someone else from logging in.

Also worth noting is they haven't ruled out kicking people who are AFK. They have openly said they are considering it but are waiting to see what the situation is like after the hardware upgrades this week.