There's two basic motivating impulses for a playoff:
1) you want to know who was the best team in a given year, based primarily on the results of the regular season, and the playoff adds a final data point to fill in gaps and/or otherwise generally inform those results.
2) your primary interest is in having a big, exciting championship tournament with wide representation by regular season participants. The regular season primarily serves to inform the fairness of entry and seeding to that tournament.
For #1 the participant list essentially marks who does and who doesn't have a reasonable claim to be the best team in the country based on the regular season. If we don't need any more information to determine that you were not the best team in the country this year, you're out. Model #2 doesn't really care about that. College football has always been historically aligned with #1 even in the absence of a tourney, and this differentiated it from every other major sport. We're now leaning hard into #2, and I guess philosophically I hate it. If CFB was good, it was in large part due to the ways in which it was different.
Eight teams would be better than twelve, but it never should have gotten past six, imo.