IMO theres differnt types of fans when it comes to footy
There are the fans that just love the AFL as a sport. Sure they will obviously follow a team, but they usually wont get to up and about, about rivalries etc. They just love the game. Usually the smarter football fans too
Then you'll find the passionate ones that love their club, and absoloutely hate their rivals. IMO these people dont have the greatest football smarts except for about their own club.
Im probably a mix of both as are most people. I love the sport, and I'm passionate for my club.
To answer your question no you dont need to follow a team to enjoy it, but it does help