The last two teams already play up to 15 games in a season. Not long ago it was 12. How many more are you willing to go? There's already the thought that college football players are used up and spit out by the universities to make money, would adding another round or two of games be yet another talking point? Do we start paying the players of teams that advance and play the additional games? What would you be willing to give up to add more teams, because something is probably going to need to traded off.
I just think there's way more to this than just saying man, this system sucks because more teams don't get a chance. When in reality every team has a chance, its just a really high bar.