I think the major issue is the lower youth levels. The numbers are small to start off right out of the gate. Where in the past they were (in some cases) double what they are now. When does that catch up at the HS level. There is always attrition over time, but if your starting point is low, that doesn't bode well for the situation.
There are enough people on the sidelines of games anymore to make up for the crowd missing in the seats. Why are there so many people on the sidelines anymore.
Some of that is just a small class size for a grade level. I think you will see this cycle back around. Soccer teams are full, kids are not getting to play, parents will make them do something else, football will get more kids again.