Well if you made a midweek league played on all the 3G pitches in the area this might help, flex league has been very popular but maybe a more competitive league.
1hrs games, twice a night, tueday and wednesday in multiple locations, Truro, Penyrn, Penwith, Falmouth, Hayle etc the 3g pitches mean you don't get games cancelled so much in winter.
Or maybe had more Saturday or Sunday morning matches. I think football can take up to much of peoples weekends.
Football will always be popular just need to find a format that works for the masses and those that are dropping away.