The criteria, as pointed out above, is not overall record and/or winning the conference championship, but more of (not in any specific order) ticket sales, attendance (sellouts) at home games, on the road following, TV ratings. It rewards in some cases teams that don't belong.
Bama didn't play in the sec's CCG last year and were put in. tOSU was in the year Clemson won the NC. Wasn't that one of the original criteria, winning your CCG? I didn't watch any of the playoff games with Bama in it, didn't watch the one tOSU played in either. But, there you have it...a good idea that's been totally jacked up. Better system is to do away with the polls and the selection committee and put in the conference winners. But then we get the 4 slots available for 5, Power 5 Conference teams and or Notre Dame.