If the goal is to have as competitive as games a possible, you're right. Expanding a playoff likely won't do that. But even good teams like Oregon and Tennessee just got waxed. No one argued Oregon shouldn't be there and most thought Temnessee deserved a spot. It's impossible to predict.

The bigger issue is the principle of access and sport. Rankings, while heavily influenced by the objective results of games played, are ultimately a subjective metric. Find me another sport on the planet where the path to a national championship is based on anyone else's opinion and not by objective standards. In every other sport if you win your conference/division or finish high enough in the standings, you make the post season. Do you or I think some mid-tier NBA team or the basketball conference of the MAC will actually win the whole thing? Absolutely not. And historically we would be right. But our opinion has nothing to do with the matter, they met the criteria and they get their shot to prove it in the field of play.

College football is different. Most teams have to go undefeated or only lose 1 game and then hope a committee chooses them to participate. Other teams can lose 2 or 3 games and still be considered because they are collectively thought to be better still anyway. And collective opinion is probably right more often than not. But there is no objective "if you do this, you're in." Inviting all conference champions fixes this.

I agree that expanding would likely add more games that aren't overly competitive. I agree that the sunbelt champion is never going to be good enough to win it all. I disagree that my opinion, your opinion, or some committee's opinion should matter an ounce in determining who gets a chance. Yeah there would mostly be blowouts. Why is that such an abhorrent thing? Fine. Let them be blowouts. Hasn't hurt any other sport, doesn't mean Oregon didn't deserve their chance this year, college football will still thrive. But create an objective system where every team has a clear path to the championship that is solely decided by the field of play, not people's opinions. It's the principle of competition and letting the sport be settled on the field of play that argues for including all conference champions, not the competitiveness of games or if a team is actually capable of winning it all.