The biggest casualty of the CFP aren’t regular season games, it’s conference championship games, which now are often pointless. If you can lose the conf championship and still make the playoffs and win the NC, what’s the point? Never loved conference championship games anyway.
Ohio State v Michigan will always matter because it’s horsefeathers Ohio State v Michigan. Same with most other rivalry games.
there are downsides to having a playoff system but the upsides are: you get a lot more meaningful fun football and you don’t have to live through excruciating debates about who the best 1, 2 or 4 teams are - you see it on the field. Which is the best and most fair system.