Anyone left out should have won their conference championship. It is as simple as that.
We went far too long with teams winning their conference and even going undefeated and being denied the opportunity to play for the national championship. Those teams legitimately got screwed.
Even with the Big Ten/SEC bias, this system is so much better than anything we have ever had. Complaining about who does and doesn’t get an at large bid is just a waste of energy.