Websites need to be up-dated more/quicker, some fields are running websites that are years old and don't show recent pics of games (it's ok keeping your price list up to date, but I want to see that your popular and well run as well).
Food needs to get better, cheap hot dogs really don't impress.
Sites need to sort out proper toilets, changing rooms, and if you can, showers. Maybe throw in a locker system for the safe keeping of keys, cash, phones. (Not all sites do this) I know that all costs money, but getting changed in to playing kit whilst stood in the open (in mud) puts people off.
The price of paint will always put the punter off, till it comes down to £80-£85 a box (or less) then it will always struggle to be seen as a value for money day out.
I would pay a bit more for the above even as a walk on.