I'm level 6 and can charge 1 maximum for association, 2 means empty stadium. I can charge 9-10 right now to fill for league games at ≈15k attendance

So your captain might be way undercharging for league, or maybe stats like win-loss record, league/ cup titles etc. mean he can't charge as much as I can, and neither of you can charge even 1 to fill the seats. The "old version" has a club fans stat that clearly takes those things into account, not just level and stadium or facilities.