This reminds me of the basketball arguments in the late 2000's when we had a couple of season where multiple players were out or hobbled for extended periods, (Scoop Jardine played with a stress fracture he told no one about because we were down to 6 scholarship player, and we went 24-11 and then 21-14. People, especially Blue Curtain, wanted Boeheim fired and considered injuries an "excuse" as if they were somehow irrelevant. "You're supposed to have depth."
Starters star because they are better than reserves. The reserves are either not as good or not as experienced or physically strong because they haven't been here as long. If you can't play starters, you aren't going to be as good. And in a sport that requires as much co-ordination as football, a kaleidoscopic line-up makes a team much less efficient. Also, the reserves, especially guys who might otherwise be red-shirting, don't get the reps in practice. if they are suddenly thrust into games, the learning curve is going to awfully high. And when guys who were supposed to star push themselves in there with injuries, they are obviously not going to be as good, either.
But if your agenda is to get the coach fired, why pay attention to any of that?