The lack of diversity at the top started manifesting itself when we went to 4 teams from 2. If we go to 8 it's still going to be more or less the same teams. If I'm a fan of Ohio State I would absolutely love that. Instead of making 4 of the 7 playoffs thus far, they'd have made 7 of 7. And then they get to do it on the field, which when you have a roster of players that is bigger, stronger, faster and deeper than 98% of the other college football teams, you're gonna have a distinct advantage over anyone except a very small handful of teams.
I guess people thought it was cool when teams like BYU, Georgia Tech and Colorado were winning titles. I'm guessing they'd have never been able to do that in a 4-team playoff format, much less an 8 or 16-team format. Those three teams "won" their titles by beating unranked Michigan, #5 Notre Dame and #19 Nebraska in their bowl games. They didn't have to play and beat the best teams, that is the only reason they were able to "win".
The problem is the same teams get the very best players every year and I don't see how you stop that. "Hey, come to my school, we have a chance to make the playoffs every now and then" or "hey, come to my school, there's about a 75% chance we'll make the playoffs every year." Where are you going if you're some hotshot recruit? Answer....the same place you'd be going to now.