simply by counting. I would happily, at my own expense, travel to all games and sit in the booth and count players on the field on every play. Last night I could have alerted coaches we only had 10 men on the field and maybe calling a timeout there to fix it would have gotten us to OT where we win the game.

There are not many things where you can expect perfection. Players will get mixed up and miss a gap assignment, run the wrong route, read a defense incorrectly, etc...But having 11 players on the field for every play is a reasonable ask for a team to achieve.