It is a familiar field — all four participants have previously made the 7-year-old playoff system. It’s the sixth appearance for Alabama and Clemson and the fourth for Ohio State. Of the 28 all-time playoff slots those three teams (plus Oklahoma) have taken up 20. (Notre Dame is making its second playoff appearance.)
Only six teams have ever won a playoff game, with LSU, Georgia and Oregon joining Bama, Clemson and Ohio State. Only LSU (last year) has won a title other than the big three.
The lack of diversity at the top has proven problematic for the sport and frustrating for fans (especially of other teams). It feels like every year you can pencil in Alabama, Clemson and Ohio State and the entire season boils down to who gets to be the other guy.
Even worse, since the selection process is subjective, the past actually matters. And since top recruits naturally want to compete in the playoff, postseason success appears to beget even more postseason success by expanding the gap between the select few powers and everyone else.