It's hard for the committee to actually just put in "4 best" since that clearly introduces the subjective nature of evaluating teams
The reality is college football is just a hard sport to find the right solution to given the size, variance in conference difficulty, etc. And it's hard to actually decipher the gaps in conference since all the games are played within conference for the most part aside from exhibition games (bowls) that have little meaning, and then the occasional marquee OOC game -- but those are early in the season when teams haven't rounded into form yet
In "theory" you'd want 4 undefeated power-5 conference champs, but I think anyone who has followed the sport knows that Washington and Florida State are not true top 4 teams. Very rare that you'd ever get the 4 best teams all being from different conferences
They have historically gone with the 4 most-deserving teams, and the result has been lopsided semifinal match-ups for the most part.
I agree that it's better for the sport if it's just "4 best" teams, but that is hard to conclude and justify, and kind of takes away incentive and value for conference titles
Obviously the format is changing, but this sport will never be perfect