Well I think that's more a function of #of regular season games than the expansion of playoffs. Really before this summer I never thought about 12, always thought 8 was good. But reading about it more and more and seeing how it would have played out from 2014 made me like it more especially with the opportunity if afforded lower status schools who might have a dream season.
Are NFL games any less fun when the playoffs expanded. Still the most watched regular season sporting events out there. There are 17, used to be 16 and I think before that 14 maybe. So it's still a relatively small number so the games are still fun and meaningful since there are so few. Every one of them still has importance. CFB there are 12 so again a relatively small number, so they still have meaning. When you have 30+ regular season games like in CBB or the other major league sports yea the regular season has less meaning. But the numbers for football are still low so even if the regular season takes a little hit, I don't think it's that's much. Games might be more for seeding and byes like the NFL but that doesn't make them that much less fun to watch.
If today was in a 12 team playoff. MIchigan might be playing for seeding but Iowa would be playing for qualification. Baylor/Ok. State...Ok State maybe for seeding, Baylor for qualilfication. Pitt/WF for qualification. Utah/Oregon for qualification. Teams playing for their playoff lives and that's fun IMO.