This pretty easy:
1. Sell alcohol. It is probably better to do controlled sales to those who aren't intoxicated. I don't find NFL, NBA, etc worse off than any college event through legal alcohol sales. I personally think it would reduce the consumption of hard liquor and curb binge drinking since people need to get toasted before the game.
2. Make food affordable. Food doesn't have to be cheap but it doesn't have to be expensive. Disney sort of has this philosophy (at least when we went about 5 years ago). Should be slightly more expensive than McDonalds.
3. Create a kid zone for people with families. These are future hawk fans. See the first link at terrible kids activities. See the second link for the royals.
https://iowacity.citymomsblog.com/2017/09/19/hawkeye-football-kinnick-kids/
https://www.mlb.com/royals/ballpark/outfield-experience/activities
4. Back off police presence: If you're not a threat to yourself or others and you're not pissing in public leave people alone. I gave up season tickets about the time the crack down was getting worse. No need for U Iowa cops (not local sheriff or ICPD) to patrol 3 blocks off campus.
5. Boot high donors and their RVs from lot next to stadium. Yes it generate money but that has to be converted to create a game day experience (kid zone, players arrival, marching band).
6. Bring back the Scottish Highlanders
7. Let fans create some of the experience. See almost all MLS games. Here is an example of KC's cauldron. They bring instruments, signs, flags, etc.
8. Audio/visual experience- Drop AC/DC. Half the band is dead or dieing. Stop all the ads in the middle of the game. Show instant replays.
9. Finally, schedule some interesting match ups in the preseason.
You need some entertainment and experience when you're destroying Southwest Missouri School of the Blind 30-7 on a hot August day.