It's difficult these days for kids to play multiple sports. A lot are specializing in 1 to try to be as good as they can in that 1 sport. Football is also a huge commitment, not to mention there's no guarantee of playing time. With Elder's difficult schedule, it's not uncommon for a kid to give up half his summer, go to practice every day during the season, dress for every game, and only get in a handful of plays a season. It takes a deep love for the sport and school to endure that. Official practice for the season does not start until August 1st, but these kids have been going at it lifting/conditioning/some camp days/7v7 for a couple months already. There's several players I heard of not playing that I was surprised, but when you take the above into consideration you can't blame them for whatever reasons they have not playing.
Back to your point, you are right that football numbers are generally down for most programs. It is certainly difficult to schedule freshman and jv games for Elder and the other GCL schools.